WordPress Multisite 5.5.3 All Plugins set have Auto-Updates Disabled, but they Updated themselves anyway

[wellesleyps]

Running a WordPress Multisite Installation on Version 5.5.3 at the time of the issue.
All plugins have Auto-Updates DISABLED (I like to run them only when I have time available to troubleshoot in case something goes wrong.)
However, on December 14, 2020 (coincidentally at the same time as the big Google outage) - All 14 of my plugins that had updates available automatically updated themselves, even though I had all auto-updates disabled. This caused my site to get overloaded and go down, which was a big issue since google was also down and made it hard to communicate.

I have since updated to WordPress 5.6, and run other updates manually (core and themes), but I cannot figure out why the plugins auto-updated themselves. I suspect it could be a multisite issue. Some plugins are network activated and others are only activated on one site. The core and themes did NOT auto-update only the plugins updated themselves.

I am very nervous that it could happen again and cause downtime. I need to be able to plan ahead and control the update timing to occur on a slow time of day. Not sure if others with multisite installations have experienced the same.

Thanks!