All the gyms use 2 types, but the mix of types varies by version. Example: A fire/rock gym with 3 trainers with 2 Pokemon each, and the leader with 4 (10 total). In X version, maybe 4 of those are straight up fire, 4 hybrids, and 2 pure rock. Meanwhile in Y version, you'd have 4 rock types, 4 hybrids and 2 fire types.
Another day successfully wasted. "I need a new quote for this signature." - Me