While it may not be “game breaking”, it is unbalancing enough that it is disallowed for Adventurers League play (same as the Aarakocra PC race, which also grants flight):

All sidebars and optional rules in the Sword Coast Adventurer’s Guide are legal for D&D Adventurers League play with the exceptions noted below.
The following rules options are either not allowed, or are restricted in some way:

The “Winged” option granting a fly speed for tieflings is not legal for D&D Adventurers League play. Cosmetic wings from the “Appearance” option that don’t grant a fly speed are fine.

As you noted in your question, flight is an ability that usually only comes available at higher levels, and usually for a limited duration. Being able to fly enables you to bypass all sorts of challenges that ground-bound PCs face.

Many monsters (especially at lower levels) lack flight, so unless they have a ranged attack, they can’t touch you
Difficult terrain is no harder to fly over than flat ground
Heights and falls are no longer a threat