Should a "good" Ph.D. student still get some strong supervision? I am getting closer to the end of Ph.D. studies and in some months I expect to stop the research to seriously work on the thesis. My supervisor has two other students working on slightly different fields than mine. He is involved in many projects and loves to help other people.

I think he trust me deeply, sometimes he tells me about his issues with his other students/people he is following and when I have chance to attend their seminars I understand that they require much more supervision than I do.

We keep talking, off course, but in the last months he welcomed every my initiative without critics. I prepared three conference papers and he basically only corrected few typos, while other people gave me more constructive comments (together with compliments) that boosted the quality of the papers. Getting closer to my defense I would expect a bit "stronger" supervision, maybe some suggestions on how to polish my work. Overall, I am still a student, not an independent researcher. I am worried that at a certain point he may examine my work with more attention, spotting some bad holes and that this may happen too late to properly fill them.

This doubt is stressing me quite much and I think that is also starting to have some negative impact on my productivity. Should I somehow address this issue to him?
Some advisors have a style of viewing supervision the same way ER doctors look at treatment. The key word is triage. Where there's a need to make things okay, he/she will be there. My advisor had the same viewpoint as he was very busy with other work and saw our meetings more as a checking-in as a friend than supervision.  I thought that when all the other students graduated, he'd give me the same amount of time as they got, but that was untrue. He continued with the same amount.

I asked him about this at the end, and he just said there weren't many crises (there was exactly one, in which he met me within 8 hours to make a game plan with me). Rest assured that your advisor probably is allowing you to create your own research programme and become independent earlier than usually scheduled. This will help your letter from him. From having more of a mentoring friend instead of being strongly supervised, I had an easy transition to postdoc, which is basically how your advisor is treating you now. In my fourth year, I felt almost abandoned. A year into my postdoc, I see that my advisor was the best advisor I could have asked for. 

Seems like you're doing great as an independent researcher and your advisor will give you his input if needed but is curious what you'll come up with on your own. A loose leash is a good thing if you're self-motivated.