Anecdote from my online Old School Essentials game: I keep all the PC character sheets in a shared google doc (template here
). This is because for half the players I sort of have to manage their characters. I can't tell if these players can't be bothered because they assume that I'll manage everything, or because OSE is somewhat new (though it's been like 10 sessions at this point), or for some other reason. In any case, with a system as simple as OSE, it's relatively easy to tab over to their sheet, if somewhat annoying. Anyway, in the last game, I had to call for various saving throws, as you do. The players who have a difficult time with the rules might take a minute to find their saving throw info (even though it's easy to find), so I end up tabbing over and saying you need to roll 15 or above on a d20. In that moment, I could say anything. I could make it an 18 or a 12 or whatever, and the player would just go with it. And it's not like the design of old school saving throws is some infallible work of design genius; if I changed save vs spells to start at 16 it would only matter 1 out of every 20 rolls.
Point is, saving throws in OSE are a player-facing mechanic, and yet for half of my players that consistency doesn't really matter. They are relying on me to tell them a target number, then they roll some dice, and we figure out the result. I get there are some players where rules consistency really matters, but it should be acknowledged that for many players it doesn't, because they barely manage to learn the rules in the first place.