I purchased a license of a proper antivirus software to avoid that bug and the performance issues gone away.
When you install another AV software, Windows Defender steps down and leaves scanning to the 3rd-party security solution. I selected one of the most lightweight ones I could find. It has been a net win for me.
One shouldn't need to do this, but it has worked so far, for years now.
Sophos does this on my work laptop with depressing regularity. At this point I just go grab coffee when the fans max out, cause I know the disk is similarly pegged and it'll be about as snappy as a bogged down Windows 98 machine until it finishes.