Hi, sorry for delay in answering...
I don't understand if reported MAC Addresses are real or were modified ad-hoc...by the way...the the one with lower value (mac-address 548028-800000) appears to belong to VSF Member with id 2...since both VSF Members own the very same priority value (left for both at default 128) I suspect that the VSF Member 2 owned the VSF Commander role when you powered off it [*] (you can check that by using the show vsf and show vsf detail CLI commands)...in that case if the Commander switch (id 2) was powered off then the Standby switch (id 1) should have taken over as the new Commander for the entire stack (the VSF Fragment contaning the Standby should indeed remain active)...and that should have happened without causing any Standby member reboot...so, to answer your question, no...it is not normal that powering down the Commander member the Standby reboots.
In any case a MAD (for VSF Split scenarios mitigation) should be setup and verified. Are you using OoBM interfaces to perform that or what?
[*] bur you never said us WHAT VSF Member id had the switch you powered off (you simply wrote us you powered off the Commander...).