I did a little digging around the code base and found that Non-Client DPI Scaling had been implemented but turned off due to the bug report T51959. (Commit rB0584c5ba8e73).

I should have highlighted the case of moving from Low DPI to High DPI in my initial report, since that would have more clearly demonstrated the hampered usability. The case when moving from High-DPI to Low-DPI still results in a bigger than necessary Titlebar which eats up valuable vertical space.

In T67017#723396, @Harley Acheson (harley) wrote:

Therefore the "error" is that the titlebar of Blender is staying at it's minimum size and not getting larger as the monitor scale increases. It is never that it is larger than it has to be, but remains as small as possible. This only seems like a good thing.

@Brecht Van Lommel (brecht) Thank you! I had indeed set the spacebar to search. Reverting it to Play fixed the issue.

@zdy (NGENNGT) I Looked through the different option in Edit>Preferences but couldn't find any option to enable/disable Keyboard Shortcuts in Tooltips. I may have missed something and would like to know if such an option exists. The closest thing I could find is the option for Tooltips (in Interface), which had been enabled by default.