Can't update to iOS 13.5 over hotspot [duplicate]

In short, yes. This is how it works:

• By default iOS does not allow the download of any single file above 100MB in size using your device's cellular/mobile data connection
• When an iOS device is sharing its cellular/mobile data connection as a Personal Hotspot, that hotspot is seen as just another type of internet connection and not as a cellular/mobile data connection
• More specifically, that connection will be seen as either a Wi-Fi interface, Bluetooth interface, or USB interface (depending on your personal hotspot settings)
• Since the second device (i.e. the one connecting to the personal hotspot) is not seeing it as a cellular/mobile data connection, it can download files larger than the 100MB cap allowed on its own cellular/mobile data connection

There are a range of settings within iOS settings that you can use to manage what (incl. individual apps) have access to your cellular/mobile data connection, but these settings will not recognise a Personal Hotspot as anything other than another internet connection.

Starting with iOS 13, Apple introduced 'Low Data Mode' which you can configure for Wifi connection, so that your device doesn't download updates, sync Photos, etc. while connected to that network.