Oh wow I find that so interesting - basically it's up to the manufacturer to decide what "add 30 seconds" means and so everyone does something different, it would seem.

Tbh I think I would prefer your way, bc I far more often want to do merely 30, 60, or 90 seconds total (so just 1-3 presses of that button 🔘), whereas I virtually never want to change the timing of something after I've already started it. It probably depends heavily what task it's being used for - rewarming a drink, 90s tiny popcorn bag, 30s quick warming of food after it cooled, etc., and more importantly how routinely the task is performed.

And for that reason it would be cool if they could be reprogrammed:-). Linux has spoiled us all far too much:-).