Just to clarify, I know a scrap test doesn't tell you what will happen down the road, which is why I added that it has been done, without issue, by others. Finishes that are well over a year old, and no trouble as yet. I'm not saying it is a good idea (at least, as a general practice), but he can make up his own mind.
CMA
(Edit: You are right in that all acrylics are not equal in formula, even if they are in name. It would perhaps be better to specify the ones used by the folks I mentioned. Most, if not all, of them used either Dupli-color or Rustoleum colors.)