I too have used a number of table saws both commercial and otherwise.

Except for this one I too have never run into troubles with removing
the nut.

But once in a while you will run across a hard nut to crack (sorry
about the pun)--this was the one for me! I tried jamming a piece of
lumber on the teeth, the teeth were too fine and started cutting the
wood. I tried putting a steel rod through the gullet and supporting
the steel rod on the saw table surface and tried removing the nut--it
bent the steel rod! And all the while the nut and arbor was drenched
in WD 40, Liquid wrench you name it.

Finally the only solution that worked was to use the aforementioned
spanner that I got from Mcmaster Carr and was able to prevent the
collar from turning. So CW count yourself lucky that you never run
across such a jammed nut!