I'm confused after received the watch from RSC

[kimobebe]

I have a Tudor BB GMT 79830 with a date-changing issue, I told RSC at Dallas and they offer me to change the date function part. Because of the COVID-19 situation, it took me almost 2 months to get it done.

I don't have time to check the watch until today. I read the invoice, it seems they serviced the movement (which I did not realize). The part that confused me the most is the "acrylic crystal".

First, Tudor BB GMT uses the sapphire crystal, not acrylic crystal, am I correct?
Second, When I give RSC my watch, they did not mention any defect of the crystal, why replace it?

Anyone knows why is that? Do you have the same experience?