[gerardvivancos]

I'm not sure this is an issue specific to this update. The very same description in the Apple forums matches what happened on my work Macbook Pro (a 2018 one if I'm not mistaken) while installing a different update a few months ago.

I won't say this is not an issue specific to this supplemental update, but I'm not buying it is _yet_.

It looks like one of the usual consequences of a system update going wrong. See that the user reports that after fixing this through Recovery Mode, they were asked to install the very same update again, as if nothing had happened. This looks like a rollback.

I wish MacOS was more transparent about what actually happens on those cases. If you had to roll back, let me know. If you could not install because of any reason, let me know.

[sleepless]

Apple has historically been lacking on proper documentation. Be that on errors happening during updates or proper documentation of what exactly they have changed in software updates. They have slightly improved, but still not great.