I will say that one example for all is Abba’s “Mamma Mia” which I interpreted the beginning of chorus “Mamma mia, we are collagen” and the beginning of the second part of it “He’ll something broken hardly”. Don’t ask past me why I had to make it about intercellular matrix.
It’s really common, it’s not just you. Singers sing much more indistinctly than they talk, and it’s common enough it’s been given a name.