The new logo for the title screen has a texture resolution whose aspect ratio mismatches the previous one, and as such the texture gets scaled in order to fit the correct dimensions of the previous logo. However, this makes it so that editing the logo with a resource pack (for instance, reverting the logo to the previous one) will scale it incorrectly.
MC-261658
Title Logo is no longer scaled integrally
Resolved
Invalid
8
This is probably why the pack format changed, so likely not a bug