System Information
Operating system: Linux-5.3.0-7648-generic-x86_64-with-Ubuntu-19.10-eoan 64 Bits
Graphics card: Quadro RTX 4000 with Max-Q Design/PCIe/SSE2 NVIDIA Corporation 4.5.0 NVIDIA 440.64

Blender Version
Broken: version: 2.90 (sub 0), branch: master (modified), commit date: 2020-04-28 09:11, hash: rBa66162e1f64e
Worked: Couldn't fnid a working version.

Short description of error
When using a custom language only for Tooltips (not User Interface), some dialog labels are translated even though they are not supposed to be tooltips.

In the following example I set Japanese for Tooltips, but not for User Interface (as you can see the menus/buttons are not translated).

Quit Dialog:

Quick Favorites:

Exact steps for others to reproduce the error

• In Preferences, switch to another language than English.
• In the language options, disable User Interface, leave on Tooltips, New Data.
• Summon the Quit menu (for example by transforming the cube and hitting Ctrl+Q)