I had to look that one up. It even has a wikipedia entry. It is a bad term. Because it is descriptive, and could be used and understood so, but apparantly people use it to mean shovelware.
Initially I thought this is about literally flipping assets instead of buying them. But those assets stores are meant to be used. Why should anyone complain about them being used.
But releasing one game can not be "assets flipping", even if only stock assets were used. So yeah, the "critique" was misnomed. Should have said, boring, only stock assets. Not the term assets flipping.