There is no need to mention any reinforcement points. Any new unit added always costs reinforcement points, unless the rule itself otherwise.
BRB update 1.0 (released over 24 month ago !)
REINFORCEMENTS
Q: If a rule creates a new unit during the battle in a matched
play game and adds them to my army, must I pay for the unit
with my reinforcement points?
A: Yes (unless the rule itself says otherwise). If you don’t
have enough reinforcement points, you cannot add that
unit to your army.
A summoned unit isnt part of any detachment, it cant be on your army roster. Instead you write how many reinforcement points you have and use those to summon units. If you set enough points aside you can summon a new cherubael if the old one dies.