Then they pulled them, referencing "breaking changes" to Safari, as rumors say, because of the User agent string.

So if the problem really was the version number string, that should be easy to fix by increasing the version number instead of appending "a" to it.

However, this might not be the full story...?

Currently there seems to be no simple way to obtain the updates. But when announced, they were ostensibly fixing serious zero-click RCE vulnerabilites.

I couldn't find any official communication regarding this, so..?

[1] https://support.apple.com/en-us/HT201224