I think that may be true up to a point.
Mostly I think it's an impression from some very successful individual managers. Wenger, Ferguson and Klopp who no team would have sacked (earlier) , if at all.
Arsenal didn't give Emery a lot of time, Liverpool didn't give Hodgson much time. Manchester United haven't been super patient with Moyes, van Gaal or even Mourinho.
The Artetas decision sticks out a bit from the norm, but it's not like that other clubs are generally that much more patient. Had Artetas done a Conte he would have been just as gone as Conte was here.
Like with us, what keeps a manager in a job over time is relative success within a somewhat realistic time frame.
There's also the difference between a club hiring more of a "project" manager and more of a "win now" manager and how that influences decisions.
I'm quite happy with most of the sackings Levy has overseen. But the time they were sacked we were pretty much in "they're not going to turn this around are they" territory.
Not worried about Ange getting sacked prematurely, though can't know for sure of course. More worried about him not finding the necessary solutions.