Right, that's traditionally been because the X server has typically had a fairly large footprint, and therefore has been very attractive for the oom killer. But in the last 15 years or so, some heuristics have been applied to deliberately discourage the oom killer from killing "important things".

I install earlyoom on systems I admin. It prevents the low-memory thrashing by killing things while the system is still responsive, instead of when the system is in a state that means it'll take hours to recover.