"Crafting and Upgrades Don't Progress" while the "Game Is Offline" - What's the harm in just relying on the phone's internal clock to progress the crafting and upgrades instead?

[Egao No Genki]

I'm flying home halfway across the country today so I have to run the phone on Airplane Mode while on my two flights.
Why do we need to rely on the game server's clock to progress the crafting and upgrades, therefore need a constant online connection?

Why can't the game just rely on the phone's own internal clock to continue those progresses while not connected? Is there really any harm in that?

While traveling today, I'm crossing timezones by one hour backwards. Will that really foul up my crafting and upgrades' progress? (How come?)

I composed this post in-flight on a notetaking app, whose filename is "Future Reddit submissions" and submitted it at the airport I'm laying over in.

[Guest]

The reason is due to cheaters, even with the connection, AnB's are still riddled with cheaters.

[Travis | Support Mgr.]

The connection doesn't have to be constant. You can connect to a network, start an ability upgrade, then reconnect after the time has passed.