No, that's always been there. But as you say, nobody ever uses it, because we don't have to.
I'm stumped, sorry. I don't know why this would be happening.
I'm not aware of any setting which controls that. It sounds more like a glitch to me.
Can you click and immediately drag to make a new selection ok? Is that functionality still working?
You'd need to check two things:
1. Can you still tap to deselect with other tools, such as the Marquee Tool?
2. When you use your mouse, can you click to deselect with the Patch Tool?