I took the red pill on this one, and by going down this rabbit hole, as you are clearly doing, you'll eventually learn: "There is no spoon" and "you must unlearn what you have learned".
I am not really sure why attrition is even a thing. You don't need to do a lot of hard work. Just ignore it. Its not a thing. There is no attr
I let the players take them when they want. Murder the kings guards and take a short rest in the hall outside his bedchambers? Sure. There is a 20% chance every 10 minutes someone comes by. Oh? changed your mind. That's fine too. USe rope trick/magnificent mansion? Great thinking! here's a cookie.
Seriously. Just let it ride man, do what seems marginally feasible for the situation. Sometimes they get to face a fight at full strength, once per day every day, and face roll everything. Sometimes its a slog to merely survive the "dungeon" (castle, city block, etc) as waves of annoying mooks make what was a supposed to be a single encounter into one massive running fight (Hey, just because the DM asks, "does anyone strike the gong?" doesn't mean that you should!).
I add monsters and subtract monsters all the time as the situation demands. I don't do any hard work. I have job, thank you very much, and DMing is not it. Its easy for me to add monsters (the far door opens and a group of cultists rush in!) or subtract (With have of their number down, the cultists try to flee).
Attrition is great for an Avalon Hill Napoleonic Wargame. My 2cp, chasing attrition balance in D&D turn the game into EVE online: A Spreadsheet Simulator.