Screensize of iPhone 11 and 15 are NOT the same
Apple advertises with a 6,1" screen for both iPhone 11 and 15. The 15 definitely has more pixels (2556 x 1179 versus 1792 x 828 for the 11). But if you search deeper you'll find:
iPhone 11 has 414 × 896 points.
iPhone 15 has 393 x 852 points.
These "points" are independent of the amount of pixels.
You can see here the screen is really smaller:
11:
15:
Just so you know.. I might return the 15 and go for a plus..