Does Pokemon GO use its own type match-up formulae?

So, it seems like type match-up is very simplified in Pokemon GO, i.e. Immunity/0.25x is 0.8, same as Not very effective and 4x is the same 1.25 as Super Effective.
That begs the question: are formulae for Immunity simplified as well?
E.g. Charizard is Fire/Flying.
Fire is weak to Ground, but Flying is immune to it.
If the formulae were imitating the original games, Charizard would take 0.8 damage from Ground moves.
However, if type match-up is calculated separately for each type, using Pokemon GO's own formula, then it's 1.25*0.8=1, i.e. normal damage.

Sadly, can't check myself, I don't see any suitable Pokemon in gyms nearby. Can somebody check and confirm whether Charizard (or any other double type with a weakness and an immunity that covers that weakness) takes normal or not very effective damage?
Zubat, Golbat and Aerodactyl can be alternatively tested for the same thing against Ground moves.

If this turns out to be true, then we can equal Immunity to Not very effective in all cases.

So, it seems like type match-up is very simplified in Pokemon GO, i.e. Immunity/0.25x is 0.8, same as Not very effective and 4x is the same 1.25 as Super Effective.
That begs the question: are formulae for Immunity simplified as well?
E.g. Charizard is Fire/Flying.
Fire is weak to Ground, but Flying is immune to it.
If the formulae were imitating the original games, Charizard would take 0.8 damage from Ground moves.
However, if type match-up is calculated separately for each type, using Pokemon GO's own formula, then it's 1.25*0.8=1, i.e. normal damage.

Sadly, can't check myself, I don't see any suitable Pokemon in gyms nearby. Can somebody check and confirm whether Charizard (or any other double type with a weakness and an immunity that covers that weakness) takes normal or not very effective damage?
Zubat, Golbat and Aerodactyl can be alternatively tested for the same thing against Ground moves.

If this turns out to be true, then we can equal Immunity to Not very effective in all cases.