I have owned and played several plastic instruments.
Plastic recorders
Plastic Cornettos (zinks)
As well as plastic mouthpieces
The plastic instruments play slightly differently to brass instruments as do the plastic mouthpieces.
But then a good player can deliver great music from almost any instrument.
It does not surprise me in the slightest that Charlie Parker sounded great on that plastic instrument. The man was a phenomenon so naturally he sounded phenomenal.