Used to be pro-Superstar, but I’ve certainly had ones that are in fact to thick to go in. The extra thickness was on the backing, or the shape of the backing, and not extra braking material.
Then I wrote a pair of sintered ones off in about 300km compared to way more than that for Formula organic (which had more stopping power too). Road side pad change with pads fatter than will fit is fun 😉 They weren’t the ones where the entire material fell off, but bits did fall off due to going so thin.
Don’t know about false economy, but on a 4 grand bike, and the price of potential dental work, I choose quality and reliability over saving the price of a pint or so.
Formula do run very close to pads as standard, so there’s very little tolerance to play with. So after that foray with Superstar I always used genuine Formula after that. Now using Shimano, but only with the real thing. Can’t speak for other brands and their replacements.