Quite a lot of applications currently expect the screen DPI exposed by the X server to be 96 even when the real display DPI is different. Additionally, currently Xwayland completely ignores any hardware information and sets the DPI to 96. Accordingly the new behavior, even if it fixes a bug, should not be enabled automatically to all users.
A better solution would be to make the default DPI stay as is and enable the correct behavior with a command line option (maybe -dpi auto, or similar). For now let's just revert the bug fix.
This reverts commit 05b3c681.