My guess would be that they had done some major touchup work and mylar was the quickest way to seal the touchups in without Clear Coating.

If it had been on there for years already and they didn't want to risk removing it would be understandable

I would think either of these would be close to the truth
Bumper does seem to like using full mylar

but if I was going to do/sell a "collector quality " machine at that price
then I'd clear coat.