No. Listing it as an “Other Outcome Measure” is not sufficient, for three reasons:
The general reason is this: clinical trials are designed with knowledge about the goal of the trial. The goal being the primary outcome. Therefore, the size, duration, measurements, and all the other important design decisions for the trial are made with the primary outcome in mind. So listing something as an other outcome means you will get some information, but but it may have problems. (Because the trial wasn’t sized to answer that question, for example.)
There is also the FDA approval issue: clinical trials which are used to show efficiency measure that effiency as a primary end point. This is for reasons described above. I’ve never seen a phased clinical trial used to get approval for a drug that listed effectiveness as a secondary or other outcome. (I don’t know if it never happens, or is just extremely rare, but in either case…) It makes it hard to see how this trial could be used for eventual FDA approval. Remember, C-peptide is the official FDA surrogate end point for curing type-1 diabetes. As far as I know, it is the only one.
Finally, for this trial specifically, it is important to remember that when this trial was first registered with the FDA (in 2014) clinical trial registry, it did include C-peptide as a primary outcome. So when first described this was a trial aimed at a cure. However, the next year (2015), the researchers moved C-peptide from a primary outcome to an other outcome. So they did extra work to remove it as primary outcome. For me, that is a very clear action that shows that C-peptides are no longer the focus of this research. (No matter what is talked about.) And then we are back to the importance of C-peptides for measuring a cure for type-1 diabetes, and for getting FDA approval for that cure.