I used to be in the Photoshop layout (and I would really want to be, having to use both programs). But even if I restore the defaults, the problem persists.
And in Photoshop the shift key function changes depending on the tool used. In selection mode, it always adds to the selection which is basically the standard function of the shift key in many applications. Like “ALT” usually means to subtract something from a selection. This actually works in Krita right now.