@ScruffyDux@actuallyautistic I don't have any answers but I will say that, from trying to look into similar things in the past, it seems the cause-effect relationship of anything non-neurological associated with autism is muddied, because people still don't know any solid causes for autism (except that in many cases it's clearly genetic, but, which genes).
Tl;dr hypotonia might not even be caused by autism, it might even sometimes be part of a cause for autism, or both might even share causes.