The only thing that can prevent me from accessing htop, is a kernel panic.
Because, even if the Desktop Environment crashes or freezes (Can't even remember the last time that happened), I can always switch to another virtual console with Ctrl+Meta+F2, login and run any program from there, including starting another DE instance.
And in the equivalent of a kernel panic in windows (BSOD), the Task Manager is inaccessible as well.
edit: disabled earlyoom & started a process that continuously allocates memory, still happens; ctrl+alt+f2 doesn't respond ever (DE ofc is frozen), and a htop over ssh gives a repaint every couple minutes if I'm lucky, but is useless; just rebooted via the physical reboot button after 30 minutes. Utterly unreasonable behavior.
On Linux the DE and shell and htop is just another program so when the system is under high memory pressure those things also get swapped out and back in when they need to run. Thrashing.
If you run something like memlockd to keep vital binaries from being swapped out I'm sure you will see that behaviour improve.