Which EDR vendor provides a mechanism for testing virus signatures? This is the first time I'm hearing it and I'd like to learn more to close that knowledge gap. I always thought they are all updated ASAP, no exceptions.
Microsoft Defender isn't the most sophisticated EDR out there, but you can manage its updates with WSUS. It's been a long time since I've been subject to a corporate imposed EDR or similar, but I seem to recall them pulling updates from a company owned server for bandwidth savings, if nothing else. You can trickle update those with network controls even if the vendor doesn't provide proper tools.
If corporate can't figure out how to manage software updates on their managed systems, the EDR software is the command and control malware the EDR software is supposed to prevent.