Every scientific theory is indeed technically false. A theory is a complex of statements, and if any one of them is false, their conjunction is necessarily false. You’ll always be able to find one statement in any theory that’s not precisely true. If you only use a 3-significant-digit point estimate of the mass of some quantity in some formal derivation chain, your conclusion is technically false according to the logician. But such logical pedantry is annoying. Some of these calculations let us do stuff, like build things or run experiments. They might be logically wrong, but they are more than good enough for our purposes.