Feedback Button.onClick() behaviour from keyboard slightly strange?

UI.Button's onClick() method is called when releasing the mouse button after clicking on the UI.Button. This is fine and what I expect.

However when I use keyboard navigation, and presumably gamepad though I haven't tried it yet, it triggers when the key is first pressed down, not when it's released. There's obviously nothing inherently wrong with this but it feels inconsistent when compared to the mouse interaction.

It would be nice if these were more consistent. Or at least if the keyboard one (and maybe also one for the mouse, my googling the issue to see what people have to say about it lead to a lot of people wanting the mouse interaction to work the opposite to how it does) had a toggle for whether to activate On[UIConfirm]Down vs On[UIConfirm]Up.