Passes already in the wallet don't require you to be online. But, what I meant was that there was additional code, thus additional size for all the functionality and ui related to boarding passes, whether or not parts of it don't work offline.

At least the airlines I've worked with prefer native code and UIs for any flow that's either revenue-producing, or likely to create issues on day-of-travel. They tend to use webviews only for things that don't have to be working to sell a ticket or board the aircraft.