We discussed this amongst ourselves.
BPX.DAEMON forces you to have a tighter envisonment. Usually, you need BPX.DAEMON to do a setuid() if you're not running root.
But arstblsp shouldn't be doing setuid on z/OS. There are other things that I believe require BPX.DAEMON, but not this.
You might open a PMR with USS, asking them if they could SLIP on the BPXP014I to try and figure out why USS thinks arstblsp needs BPX.DAEMON in this particular case.
Ed