The Macintosh Finder should never give wrong information.

If the message you got looks like this

be aware that this is not about updating to Big Sur. It is an internal software update/patch that is required for the interface with the iPhone that you have. It does change the version of the MacOS you are using. I have seen this on two computers and applied the update to each with no issues (the one on Catalina took a fairly long time, 10-15 minutes perhaps).

I agree that it would be helpful if Apple provided some more context or information here, but you are putting more drama into this than it really probably deserves.

banjoboye wrote:

The default selection is install which presumably forces an upgrade to Big Sur.

Your presumption is incorrect. It is merely a patch, not an upgrade.

banjoboye wrote:

Finder message in macOS Catalina:

"A software update is required to connect to banjoe-boye's iPhone.

Would you like to download and install this update now? Use of this software is subject to the original software license agreement that accompanied the software being updated.

learn more - not now - install"

The default selection is install which presumably forces an upgrade to Big Sur.

Poppycock!

The Macintosh Finder should never give wrong information. Catalina 10.15.7 with all supplemental updates as of February 5, 2021, although still containing significant bugs, does not need to be updated to Big Sur in order for iOS 14.4 to sync by USB iPhone cable to Mac. This erroneous system message is persistent, appearing in 10.15.5, .6 & .7, dumb and wrong. Apple Fix it please.

Thank you for listening, and thanks for such persistent hard work, a long late hours that it takes to remain better than the pain and suffering that is Micr0s0ft and Andr0id.

banjoe-boye'

Mac Evangelist since 1991

you can submit your Apple Feedback http://www.apple.com/feedback