In the case of Modern Sonic "Reversion-Up!" and Silver "Reversion-Up!"
from FNaS 3: II "RoR"
(Yes, Silver is also in Fierce Forces as well, the past Phone Dude)
Even though they are also the Security Guards, but they received a special treatment and their rank is called: Sentinel Martial Artist instead just of Secuirty Guard.

Reminder:
The Night Guards from the previous pizzerias from the version:
Five Nights at Sonic's: Insane Immerse "Route of Recollect"
(changed from Widerise Mingleverse - addon story before Fierce Forces)
were taken by Silent "Avatar-On!" and upgraded to the Security Guard rank,
via Silent's "Avatar-On!" Concord Gem Bracelets and now are the summonable comrades.
They can fight back and are immune to attacks (they can't get hurt).
They stay for a limited period of time when Silent "Player-On!" / "Avatar-On!" summons them.

Also, gotta go.