Several manual attempts to run Defender in Windows 10 Pro on a Dell 7280 (RAM 16g and SSD at 65% capacity) resulted in only 15 files being scanned using both Quick and Full scan modes.
Windows, Defender and all updates appear to be current.
Defender was set for regular periodic scans. I decided to initiate a manual scan because after a restart, the system hesitated while responding to keyboard commands innocuous as screen brightening.
I can't say I've ever encountered such Windows Security behavior.
No other antivirus lives on the system. Only HouseCall has been run in the past, but not recently.
Please be so kind as to opine.