When you get a gift, you get a gift timeout. So let's say you have 150 piety, gift timeout is 0. You kill something, get a gift, you're now at 150 piety, gift timeout is 30. The next time you kill something that would give you piety, you don't go to 151/30, you go 150/29. After a couple more kills enough time has passed that your piety decayed to 149, your timeout is 15. Eventually you hit 147 piety 0 timeout, and can get another gift again. If you don't get a gift right away, your piety will go up to 148+ etc.
So duvessa is right that it isn't technically that simple, but effectively yes, getting a gift lowers your piety gain for a while, it just takes your future piety rather than your current piety.
All numbers approximate and made up, but that's the basic flow. I don't think it's possible to ever hit 200 piety on trog with a race that gets gifts - felids could. You can summon a LOT of brothers in arms before 200 piety falls all the way to 150.
But, but ... Oka lets you use UC+statue form!
True, and I've won a cheibriados felid for this reason