Issues with Iphone during first year warranty and repairment

Hello,

I've been experiencing issues with my iphone's screen for quite some time. I decided to bring it to an authorized Apple service, as it is under first year warranty. (i bought and activated the device about 7-8 months ago) I just received feedback from the service, that indeed there is an issue with the screen so they had to replace the screen and my phone is ready.

My question in place, since it is under first year Apple official warranty, shouldn't they replace my device with a new one, instead of replacing the screen? From previous experiences, I fear trusting services, even the official ones. (they have pretty low rating and bad reviews but no alternative possible for my country)

Many Thanks,

V.