Personally I can recall several instances where the female "sleeve's" on this type of quick-connect have backed out of the plastic body upon my attempt to plug them together with thier male half. Typically the female sleeve relies on to two tiny tabs 180 degrees apart to arrest it once pushed into the connector body.
Wiggling the male and female halves to get them to mate (which we all do whenever the pins don't line up perfectly)can easily result in the sleeve tabs slipping. Especially when the hole size in the body of the connector is not tightly controlled. (yeah, but don't worry yang-fu in whoflungdung china will be looking out for you....err...right?)
With 277 volt lighting especially there is no way these things are going to make me feel safe when working on live ballasts. To the contrary they are going to make me very worried and probably cause me to cut the power short of the quick connector before working on them.
my $0.02
