Author contributions include statements about experiment not conducted in study I am a graduate student submitting a computational biology paper for peer review. It is intended to be a “methodology paper” for the journal. Our paper uses new methodology to analyze several public datasets and demonstrate the use and benefits of the new methodology. There were originally two authors (my advisor and I). We added a third author (Author C) for having shared one of the datasets (data #3) with us several years ago (and it became public recently). Author C had a few discussions with us about the results of our methodology applied to data #3 and provided a few interpretations. I recently asked Author C for how we should state author contributions and two of the sentences they added were along these lines: 

“Author C planned, designed, and conducted the experiment to identify results for data #3. All authors analyzed data #3.”

I was a bit concerned by both sentences.

Data #3 is open/public. I believe Author C planned, designed, and conducted the experiment to generate data #3 for their own earlier paper, where they analyzed it using traditional methods. The current paper simply uses multiple public datasets (including theirs) to demonstrate the benefits of new computational tools. It is not about the collection of data #3. I feel they simply shared data #3 for the current paper and that we analyzed it with our own methods. If we state sentence #1, we may be expected to include a detailed methods section for the wet-lab collection process of data #3, which is really a part of their own previous paper and deflects from the focus of the current “methodology paper” (it would start to feel more like a “research paper”). At that point, it would be strange to not also include method sections for the collections of data #1, 2, 4, etc. (which are also public datasets).

Regarding sentence #2, I did not feel that Author C analyzed data #3 with us in the current paper, but simply provided interpretations based on their previous analyses of the data #3 for their own paper.

I do not plan to mention my concerns with sentence #2 as it is ambiguous, but I plan to propose to Author C that we remove sentence #1 or specify that it was for a previous paper. Is it reasonable for me to ask this? Or, when a wet-lab biologist like Author C generates data, can they add that they planned, designed, and conducted the experiment to generate that data as their contribution on multiple papers, without even including the details in the methods section of the papers themselves? Could this put them (or me as first author) at risk for appearing unethical?

I am mostly hoping to better ascertain what the “norm” and ethics are in this area, and how I can handle this situation respectfully and fairly.
This seems like a totally reasonable statement which is perfectly clear. Unless you took raw bcl files or whichever image file comes direct off the scope the other author analyzed data. Clearly they collected the data. You don't have to do anything other than cite their work.

This is a normal statement and if you complain about it your collaborator will think you're weird.