- NaN bits are non-deterministic. x86 and ARM generate different sign bits for NaNs. Wasm says NaN payloads are completely unpredictable.

- GPUs don't give a shit about IEEE-754 and apply optimizations raging from DAZ to -ffast-math.

- sin, rsqrt, etc. behave differently when implemented by different libraries. If you're linking libm for sin, you can get different implementations depending on the libc in use. Or you can get different results on different hardware.

- C compilers are allowed to "optimize" a * b + c to FMA when they wish to. The standard only technically allows this merge within one expression, but GCC enables this in all cases by default on some `-std`s.

You're technically correct that floats can be used right, but it's just impossible to explain to a layman that, yes, floats are fine on CPUs, but not on GPUs; fine if you're doing normal arithmetic and sqrt, but not sin or rsqrt; fine on modern compilers, but not old ones; fine on x86, but not i686; fine if you're writing code yourself, but not if you're relying on linear algebra libraries, unless of course you write `a * b + c` and compile with the wrong options; fine if you rely on float equality, but not bitwise equality; etc. Everything is broken and the entire thing is a mess.