It's a neologism. Some people love it. (Actually, it seems like a lot of people do.) To others however, it strikes the ear as awkward sounding. I wouldn't say there's anything "wrong" about it. It's a matter of taste. It's a bit of a pet peeve for some of us.
I bought a book a couple of years ago: iOS and macOS Performance Tuning. I took note that the author had not used the word "performant" even once in the book's 400 pages. Maybe I'm a snob, but it made the author seem the more credible to me.
