As already observed in other threads, it seems that Avast has the habit of sometimes performing automatic updates even if the user has set the updates to "manual".
It looks like some "emergency" updates are carried out compulsorily, without the user being allowed to prevent them. It happened also to me, at least a couple of times in recent years; the last one was a few weeks ago, when I realized that version 23.12 had installed itself without any kind of request or notification. While I have always had the habit to disable all automatic updates (not only the antivirus ones).
Of course, it is understandable that certain updates may be particularly urgent and essential for security.
However, in my humble opinion, it would always be a good idea to let the user decide, for example by forcibly producing notifications with messages like
"ATTENTION! Due to serious security problems it is strongly recommended to update the program as soon as possible to the new version".
Or, at least, with a notification like
"ATTENTION! Dear user, due to serious security problems we have exceptionally forced the update to the new version; your setting regarding manual updates, however, remains in force".
Providing such notifications, which would prevent any misunderstandings on the issue, should be very simple for developers.
And I (respectfully) wonder why it hasn't been done yet.