Is it possible to uplevel during team transfers in any of the FAANG companies?

Very rare, but I've seen it happen a few times. It's not something you can actively aim for since the dynamics of internal transfers are pretty unfavorable to begin with (they are usually blocked, take a long time, or at best land at the same level and pay). It mostly depends on how much pull your sponsor has.

My friends and I used to joke that it's easier to get promoted by leaving for a few years and applying to a higher level position at the original company. Unfortunately, it's closer to the truth than a joke.

I'm sure it has happened in some super obscure case, but I'm certain that 99.9% of cases resulted in the person either keeping their level or going to a lower one (this will happen when folks from outside of SWE switch into SWE).

I talk more about this here: "How can I best switch internally and uplevel?"