Yes, Duck, using the Mothership's recommended filter(s) would have avoided this. As I buy whichever filter on the shelf fits a K-75 (and my cup socket), I have used a variety of them. I am prejudiced against Fram.
I think I now know what happened. The gasket on the 'failed' filter sits nicely on the housing flange -- which is all I looked at -- but, rather than lying flat against the filter base it sits in a circular groove, stands a few mm proud and wants to be compressed. My 'snug plus half a turn max' ritual was probably insufficient to make a seal. I simply did not tighten it enough!
If this is the case, my situational awareness and readiness to adapt are again kicking in after the need. As Sherlock said, "the last possibility, however unlikely, must be the solution". I'll see next oil change when I crank it down. Thanks all for trying to help.
By the way, even Wile E. Coyote succeeded eventually.