That's not the OS bloating as much as it is the "System Data" bloating. That happens over time. If you had, prior to installing the iPadOS 17 Beta OTA, done a DFU restore to whatever the then-current version of iPadOS 16, you wouldn't have had so much in "System Data" eating up that space. But yes, to your main point, you'll fill that space with "System Data" much faster when you have less storage to play with from the beginning.
It’s both. On the iPad 6th gen running iPadOS 14.8.1 is 6GB while 17.5.1 is 9GB.
On my devices, Other/System Data is often OS size +/- 1-2GB.