Hi Michael,
sorry for my late reply. I noticed this behaviour on a temporarily but fresh installed Ubuntu host. So I first contacted the Ubuntu team, which confirmed my issue, but pointed me to Debian team first. I already reported your feedback (i.e. this thread) back to the Ubuntu team and they opened an Ubuntu bug now (see: https://bugs.launchpad.net/ubuntu/+source/freeradius/+bug/1752156). But also regarding the debian package, I do not see the benefit of having mode 2751 instead of 2750. But please feel free to correct me, if I have overlooked something. Best regards and thanks a lot Simon