Real BOTs are more and more using whatwg cartel web engines, namely this has an end. If not all, namely the end was already reached. The ones not using them are more likely to be shadowpaid hackers by the whatwg cartel to ruin anything noscript/basic HTML (or they could be beyond idiotic hackers, unlikely).
Not to mention, many "maths challenges" out there are nothing more than a 'wait loop' in the end. Namely, you could replace them with a HTTP hard refresh timer with human scale wait times in order to get the same pertinent result. Those are actually even worse because they are pleasing the whatwg cartel since those are made to work only in their web engines.
The least they could do is to standardize those 'maths challenges' and make them HTTP header friendly.
Human scale wait timers aren't a big issue for bots. More parallel requests. Or more websites being scraped in parallel, if the website doesn't allow multiple timers going at once.
Whereas number crunching actually ties up some CPU time.
Ofc a timer will be set per connection and has to be only one part of a whole global and probably fine-grained connection policy !
Their only purpose compared to such timer, is, in their current state to create a hard dependency on exactly the web engines of the whatwg cartel and do exclude low end hardware (this does create a barrier of entry for new hardware or small hardware).
At least, they could have had the decency to design some "HTTP" specs to de-couple those maths challenges from those abominations which are the web engines of the whatwg cartel (maybe that's the case).
Yep, I could bet that a lot of BOTs are now based on those abominations (and probably using neural nets). You also have click farms with real humans.
There is so much wrong there... well Big Tech...