Any timer is constrained to the resolution set by the system timer. To go lower one would require something akin to a spin-loop, which defeats any gain by keeping the resolution high.
setTimeout(,0) is a special case. It means "make this function be ran after the current call stack clears". That requires neither a timer nor a spin loop.
Right, but that precedent was only set by incorrect implementations existing in the first place. Using setTimeout(,0) recursively in lieu of (a then unavailable) requestAnimationFrame or a non-zero timeout period is in my mind equivalent to while(true){}/infinite tail recursion.
Probably heaps, but why would that cause the system-wide timer to run more frequently? Even if it does need to it should only be temporary.