EDIT: after googling around, it seems to actually be an issue with macOS. I noticed that pinch to zoom is broken for all apps (native and 3rd party). I had to go to System settings > trackpad and disable, enable pinch to zoom for it to work again.
EDIT: after googling around, it seems to actually be an issue with macOS. I noticed that pinch to zoom is broken for all apps (native and 3rd party). I had to go to System settings > trackpad and disable, enable pinch to zoom for it to work again.