All iMessages downloaded to iPhone from iCloud filling storage

so here’s the timeline of events:

1) iPhone was IOS16, with messages only taking 1gb, all data was offloaded to iCloud.

(messages set to save for forever and iMessages for iCloud was turned on)

2) updated iPhone to IOS17 and Apple Watch to watch 10

3) next day, all iMessages were offloaded from the iCloud back into the iPhone taking up 15gb

(Settings for messages and iCloud did not change)

4) turned off iMessages in the iCloud

5) set messages to be deleted after a year

6) turned back on iMessages to be saved in iCloud

7) received error about being unable to change messages being set to deleted after one year due to a different device having different settings

I'm not understanding what the issue is and why updated my iPhone caused this to happen. Any fix?