I've just installed the update, and the inconsistency between the countdown timer start button and the stopwatch start button are probably deliberate. I didn't think about it at the time, but starting and stopping a stopwatch should have as precise a timing as possible, adding a fuzz of a "pressed" state for buttons which can respond instantly will reduce accuracy of the stopwatch. But for the countdown timer, accuracy doesn't matter so much, and these buttons work like normal ones, with a pressed state.

So, rather than evidence of bad design, this could be evidence of good design.