Reclassifying safe harbor match contributions?

A plan sponsor is looking to adopt a retroactive amendment effective 1/1/25 to change their safe harbor match plan to be a safe harbor nonelective (3%) plan, primarily because of the gateway test benefits for their profit sharing. Are they legally allowed to reclassify the safe harbor match contributions they made from 1/1/25 to now as non-elective, essentially using it as a kind of credit when they true up at the end of the year? That would result in everyone having gotten a 3% contribution for the plan year. On one hand, my instincts say that adopting the amendment as of 1/1/25 would mean the safe harbor match provisions would no longer have been in place, so it wouldn't have to stay as match, but on the other hand it feels like it could be sketchy as it was made under a different contribution source structure. Anyone have insight on this?