Most likely there has been no such change. You've just started paying attention to it for some reason. Looking at a couple of data sources for popularity of terms over time, "birth parent" has been consistently more used:
So if a family provided eggs & sperm and had a surrogate to give birth on their behalf, then later gave the child up for adoption, how would you identify everyone?
Also, I'd assume the child would later look for those people with their genetic material, their biological parents, those who provided the sperm & eggs. Not the birth parent, who birthed them. There's much less of a connection there as it's the person who simply carried them for a money transaction and is not part of the child genetically.
Why are you asking me? I don't give a crap about that.
You made a statement on this being a new term, I gave references showing it was factually incorrect. The proper response is "thank you, I was wrong", not whatever this thing you responded with is.
https://books.google.com/ngrams/graph?content=Biological+par...
https://trends.google.com/trends/explore?date=all&q=Biologic...