I had a look at the logs and although the vehicle did lean back quite a lot (to 45degrees) I think it did eventually detect the landing and disarm. My guess is that it just got unlucky and it landed a little bit off the target as it touched down and then it fought harder and harder to try and get back to the target by leaning over.
In the graph below the blue line shows the PSC.TVY (position controller target velocity in east-west direction) we can see right from the beginning it’s off from the actual velocity (PSD.Vy in orange) and this builds up (this is velocity controller I-term build-up most likely caused by slightly off position vs the target).
I think the 3.6.7 change was not relevant in this situation because the AC_Loiter::soften_for_landing function is only called when “land complete maybe” and we log when “land complete maybe” becomes true and it’s right at the end of the log after the leaning has already happened.
Re the ReleaseNotes that last entry covers both 3.6.7-rc1 and the final 3.6.7 release. The two were the same except for the name.