no, in both cases the trunk failed. the basswood broke 10' below my feet while I was cutting the top out of it, thankfully my life line was to an adjacent sugar maple or Mama Spracklin woulda been minus one son as i was about 70' off the ground.
and yes the weeping willow trunk failed when i was using a technique called double crotching, where you essentially have two tie in points, i was tied in around a 10" stem for my primary line , and due to the angle i needed to work, i used the tail end of my life line to tie into a secondary crotch that was about 6" diameter. the 10" stem buckled and had i not had the secondary tie in, i'd have been doing an impersonation of a pancake.
ive never had a crotch failure from a lifeline, but have seen crotch failures from excessive rigging loads.
in general i'll happily tie in my lifeline on a trunk of a hardwood that is showing no signs of defect as small as about 4" in diameter, some species i can get away with smaller like honey locust or hickory, down to about 2.5-3" in softer deciduous trees like silver maple that are know for weak branch unions, i'll pay a lot more attention to the branch union. in stuff like linden/poplar/willow/whitepine 6" minimum. i'm 6' and 225... 20 years and 20(or maybe a few more) pounds ago, id tie into smaller stuff.