Yes, I have been guilty of this before. This won’t be an issue for many games, but it’ll happen every now and then. I don’t remember the videos in question, though sometimes I’m guessing I was just too eager and clicked “bet” when I shouldn’t have.
Otherwise, it depends on the game. You can (and should) use a small voucher to check for plays on games such as Buffalo Link or Phoenix Link, for example. But for plenty of other games, as you alluded to, you won’t be able to check for plays if the voucher is smaller than the bet amount. And of course, for many other games, you won’t need to insert a voucher or money at all to check for plays.
It’s really not all that many games where this is a concern, so I wouldn’t overthink this aspect of slotting. But keep the questions coming. This is a good question on something I never really gave much thought.