Not everyone at Google has a Mac? Nobody wants to reinstall GBus every 3 days?

Seven days.

Why would you have to reinstall it every 3 days?

IIRC dev certs expire quickly, by design

Free certificates expire after a week. Standard certificates obtained from a developer program membership last for a year.

Yup. However, at least you don't really need a Mac for that, as there are external tools to resign and install ipa files.

Probably something like this:

XX% of Google employees are non-technical

XX% of Google employees don't use Mac as their laptop platform

XX% of Google employees have a locked-down Mac that isn't allowed to run XCode or locally-compiled binaries because their job role isn't in Engineering

From what I understand, it actually is a public app:

https://www.tripshot.com/

https://itunes.apple.com/us/app/tripshot/id1007192056?mt=8

The employees would each have to spend $100 on a developer membership (sharing them is a good way to get more revokes).

No, that's not necessarily for loading an app on to your device. It's only necessary for broader distribution.

You can only sideload up to a certain number of apps (3 IIRC), only for seven days at a time, and only using certain APIs (cannot for example use notifications), all of which would pose serious limitations.

60,000+ employees makes this unrealistic.