UMMMM, not really.
Gag bits have leverage, but are not curbs.....
Dutch jumper (ring) bits have leverage, but are not curbs.
Elevator bits have leverage, but are not curbs.
These both use leverage to pull the crown piece of the bridle onto the poll nerve, not the jaw. Kinder than a curb, IMHO.
I don't like argentines because they have all the severity of both curb and snaffle (nutcracker action on jaw) but none of the kindness.
However gags do pull up in the mouth the mouth piece sliiides. Making it not a curb. Like so