It's a very frustrating experience if you have to log in twice, even more so if two-factor authentication is involved. https://webkit.org/blog/14205/news-from-wwdc23-webkit-features-in-safari-17-beta/#:~:text=When%20a%20user%20adds,is%20great%20for%20privacy.
<rdar://problem/110763629>
The fix for this issue is outside of the WebKit Open Source Project. Changing to RESOLVED | MOVED. This work is now tracked by rdar://104438319.