Linux had many similar restrictions in its lifetime; it just has a different compatibility philosophy that allowed it to break all the relevant ABIs. Most recently, dual-socket 192-core Ampere systems were running into a hardcoded 256-processor limit. https://www.tomshardware.com/pc-components/cpus/yes-you-can-...
Tom's hardware is mistaken in their reporting. That's raisng the limit without using CPUMASK_OFFSTACK. The kernel already supported thousands of cores with CPUMASK_OFFSTACK and has at least since the 2.6.x days.