In the middle of framing my basement, I realized I made a rough opening for a bathroom door approximately 4" too big. I glued m & screwed in another 2x4 to each jack stud to get the opening where it needs to be. I have PT wall plates for all walls but I got to thinking, do these new 2x4s need to be PT due to their ends in contact with the concrete? It's an interior wall. I really hope not... thoughts??
No need for the jack studs to be PT, In a basement that has no water or moisture issues, using PT material for plates is just a precaution, not a necessity, IMHO. This has been my experience in demoing older work while remodeling. BUT for what its worth, hold the jack studs up off the floor a little, say 1/8" just for the heck of it. If I think about it, I set a little construction adhesive where the end of the jack stud goes and set the end in the glue to bond it to the floor and seal the end. If you have the studs set, do not sweat it.
You need to isolation non pressure treated wood from contact with concrete. This is code and you want to do this to prevent future issue with decay.
Because of your very solid attachment of the spacer stud to the trimmer stud, you do not need to support the bottom of the spacer stud by attaching it to the floor. Also, it is not necessary to fully extend the spacer stud down to the floor for attachment of the door, dry wall or door trim, just to near the floor.
In your case, isolating the wood from the concrete is very simple to do, just cut in a gap between the end of the spacer stud and the floor. Noting the lack of a need to extend the spacer stud down close to the concrete allows for options to cut it. I would personally just run a skill saw over the face of it with the guard on the concrete and the blade set to the 1-1/2" depth of the 2x4. Don't hit a screw of course.