As part of the March 2018 Security Updates Microsoft have quite quietly announced that the AV compatibility checks that previously stopped devices from receiving updates have been removed for Windows 10 devices.
This means that Windows 10 devices will continue to recieve security updates (unless they have a known bad AV Driver). Previously they wouldn't have recieved any security updates, nor be aware that they were missing updates.
Here's how Microsoft have worded it on their website:
March 13, 2018 Status Update
Our recent work with our anti-virus (AV) partners on compatibility with Windows updates has now reached a sustained level of broad ecosystem compatibility. Based on our analysis of available data, we are now lifting the AV compatibility check for the March 2018 Windows security updates for supported Windows 10 devices via Windows Update. We continue to require that AV software is compatible and in cases where there are known issues of AV driver compatibility, we will block those devices from updates to avoid any issues.
We recommend customers check with their AV provider on compatibility of their installed AV software product.
This is good news, we'll have to wait and see what happens with Microsoft
You can read the full Microsoft article on Windows Security Updates and Antivirus Software here.