Will the research activity during my Master's program seriously impact my PhD or career path? I've posted a few questions here seeking advice on my life as a first-semester graduate student. I have a question that is somewhat related to those, and also related to this question (What happens if you don't enjoy your research partially through your degree?) but felt it was slightly different and wanted to ask my own.

TL;DR

The lab that I'm at now has recently been heavily focused on one specific field of research, and I'm also expected to conduct research activity in that field and squeeze in time to work on things that I personally want to pursue later as a more serious PhD student and possible career. Will my research being heavily focused in an irrelevant area impact my future prospects of applying to PhD programs?

Long version

I'm currently enrolled in a Master's/PhD integrated program at a Korean University. The lab that I'm at does AI/deep learning research. My personal interests lie in computational linguistics, and I made it clear to my advisor that it's what I want to pursue and I wanted to work with those in the field at his lab, which he was happy to hear. I also told him that I have plans to complete my Master's here and go for a PhD to the US. He recommended that I finish my PhD here and go for a postdoc abroad, but that he's also "more than happy to let me go if it's what you want."

Recently, he's really taken a "passion" into this thing called "AI-driven drug discovery," where you're basically using deep learning techniques to find which chemical compounds may potentially become new drug components. It's interesting and important for sure, but it's not really what I had in mind when I first came to the lab or what I imagined to be doing later in life.

The fact that 1) I'm fluent in English, and 2) I'm "technically enrolled in a PhD program" and so will be at the lab longer than regular Master's program students has caused my professor to take a liking to me and him and other senior lab mates have really urged me to at least take a look into the field of bioinformatics. I thought "what the hell, I'll give it a try and if it's not for me then I'll talk to my advisor and back out."
 It is a bit naive of me to think that backing out of  research I've been engaged in will be easy.

I've talked to other seniors at the lab about my concerns, and  they all understand where I'm coming from and advise me to "do the bare minimum to keep me out of trouble" while spending all my time and resources doing research in things I want to and prepare for applying to PhD programs abroad (publishing papers, attending seminars and conferences, etc.)

I'm still a bit concerned though, as bioinformatics is a little distant from computational linguistics. My undergraduate degree wasn't even from a STEM field or linguistics either (international relations major and computer science double major). Has anyone either been down this road, or seen anyone go down it? From a professor who's seeing my application as a potential PhD candidate, how would it look if much of my prior research is in bioinformatics when it says I want to do PhD-level research in computational linguistics?

Any tips or advice are greatly appreciated. Thanks.
The further you are in your studies, the more your track record will dictate where you go. But I think that you are not at a point that experience in a related field is going to harm you. And, if you do things cleverly, you can gain very relevant experience.

For instance, you can gain experience in a relevant programming language doing bioinformatics (which is basically open to any programming language), and this technical experience will be relevant to any computational work you do. This seems like a great opportunity to gain that experience while improving your academic track record. I believe that in both these fields a PI will be most interested in someone with technical knowledge (given that a PhD in applied CS is not a course in CS), and luckily for you, this knowledge is independent of whether you are studying genes or phonemes (sorry for that terrible pun).

It's really rare in academia to be able to do exactly what you want. You'll always be carrying out research under someone else's vision, and rather than trying to find the perfect position or such, you just need to find a way to shine in that project/position/etc. As I said above, I believe that the credit and technical experience you will gain in this current position will be relevant for computational linguistics also, especially given the stage you are at. If there is a time to diversify your abilities, earlier is better. At a later stage this will have different consequences.

So I think you should take the bull by the horns and learn as much as you can. I can't imagine someone turning you down from a PhD because of being involved in a computational project simply because it doesn't perfectly overlap their field. All these computational-related fields have a huge overlap nowadays, and computational linguistics is in itself an interdisciplinary field.