Of all the features making knee mills what they are; their quill lock might be the worst. It's conveniently placed but infrequently used. All kinds of aftermarket solutions have popped up; springs, magnets, counter-weights, none stayed on market long.
It's good its found a way into the forum.

Reversing the assembly is less common now, but an old practice.
Probably due turnover of less committed machinists, with fewer experienced mentors.