At which point I discovered that the angle-grinder switch,
which was quite stiff, had a lock-on position (why??).

I think tools without lock on power are dangerous. If I need to constant
press my thumb on a stiff switch to keep the thing going, that's one less
hand available to actually control the tool.

I would probably have injured myself with the grinder had I had to keep my
finger pressed in some inappropriate position.

I find the same with my router. It is near useless as you have to contort
your hands to keep it going, which makes guiding the thing impossible.

Christian.