Is that 5% number real or your estimate?
It's a hand-waved estimate, but let's recognize that Apple actively plans on killing support for NAS targets for Time Machine:
> Time Machine backup to NAS devices over Apple Filing Protocol (AFP) is not recommended and won't be supported in a future version of macOS.
https://support.apple.com/en-us/102423
Yeah, it sounds a bit high to me.
alt Hacker News
It's a hand-waved estimate, but let's recognize that Apple actively plans on killing support for NAS targets for Time Machine:
> Time Machine backup to NAS devices over Apple Filing Protocol (AFP) is not recommended and won't be supported in a future version of macOS.
https://support.apple.com/en-us/102423