Note, it's using tweak threshold, would be careful changing this since we might not want to have different values for tweak & drag in the event handling (could cause bugs).

Hello Brecht, and thank you very much for your explanation.
Names in this form may in fact be misleading, because, as you can see in the picture below "Click Drag" may suggest a relationship with a "Drag Treashold" parameter.
Maybe "Click Tweak" in keymap would be a better idea?

This was added to support keyboard shortcuts to be used for both pie menus and single key access.

For a while we had Tab-key access both pie menu and edit mode.

After testing we agreed this wasn't a good default because key-up events give the impression of lag, if you're not expecting it to behave this way.

But IIRC, from discussion at the time we thought this useful to be able to do, and people making their own keymaps customization could use it.

Without this there is no way to tell the difference between a click and a click-drag keyboard event:

This allows for some more flexible keymaps, OTOH, having click and click-drag on keyboard event's is not typically done.

@Pablo Vazquez (pablovazquez) - what do you think? Is supporting different actions for tap/drag (typically pie menu) worth supporting?

*EDIT* posted on dev-talk: https://devtalk.blender.org/t/keyboard-tap-drag-dection-useful/5450

Even calling this tweak-threshold is misleading since it's used for click & double-click.

Having both is confusing, propose to use only one, see: D4322

Closing since this is more a UI/communication issue,
not a mistake in the code.