I just discovered that these are "special"
As it happens my favorite test leads with the *really* sharp tips fit properly, so I never noticed the issue. But all others either don't fully seat or leave exposed metal.
So what fits? I spent a long afternoon searching without success. Either they did not fit or the drawings didn't give the critical dimension. The insulator at the end of the plug needs to be under 0.330". The ones I have that fit are 0.321" at the plug end and then taper to 0.400" at the wire end. I'm looking for tin plated 4 or 8 spring phosphor, bronze or beryllium copper in solder style.