As far as I've seen, this only happens when you help someone who is acting on the same turn as you. If you help someone who goes after you, then they still have their full actions. Thus I interpret it not as standing up costs an action, but that you've already spent your "action" making a death saving throw. Which kind of makes sense?
If your heart stopped, then someone defibrillated you, would you immediately be ready to fight (or do some other action-equivalent thing). Or would it take you at least a few seconds (a turn) to get your bearings?
Yes but then I don't have a heart so. That could be why it seems bugged to me, they way they are doing group initiative to me is wonky. I can sorta see it but it's hard telling who is actually going at the same time. yeah I know the pictures get bigger, but hell even the ai (space button) gets confused at times and skips a person. So it's not just me.