"k" & "d" isn't capitalized in "I know what I'm doing" button

Well, on this case is grammar, and on that sentence normal grammatical rules must be used. So, there is no problem.

On any of the other cases they must be capitalized because they have specific grammar rules for their cases.

Well, that's my opinion, and Mojang staff should see this.

I think this might be intended because, unlike other buttons, the text on this button is a complete sentence. Complete sentences have different capitalization rules than phrases.

It's a sentence not the action taken, feels really weird to capitalize words in this to me.