Looking at it from Europe, this definitely also happens. It depends on the situation. I know of ppl who were kept bcs the parting was in good faith (which was less a firing and more an agreement that parting is in everyone's interest), but I also know of ppl who had their access revoked before firing bcs it wasn't. The latter had unilateral system access as well, which added to it. It's not about humane or inhumane, it's about risk. The 3-6 months being nice is also a fairytale that I have only ever heard in a positive light from employees who are not particularly ambitious or awake or in any way satisfied with their jobs or the prospect of a future job. On the other hand from the perspective of employers it's consistently hard to effectively restructure, it's expensice and awkward to have to pretend to want to keep someone around that you or they don't want around.

It's just one of these rules that unfortunately in Europe allow people to view life purely as the time between jobs. I'd never tell that to someone's face but it's simply a fact that the world stops of people don't work and no matter what the ideal world looks like in your dreams, working is the only real way forward for anything. It's part of the reason why Europe is falling behind on everything.