No, what you have the wrench on is more like an adapter plug, which screws into the knuckle on one side, and the actual mounting through bolt screws into that adapter. So when you are removing the bolt, you have to put one wrench on the adapter, and another wrench on the through bolt head. The mounting bolt has to completely unscrew from the adapter in order to remove the strut.
In one of your pictures, it appears the mounting bolt is still in place, perhaps you screwed it back in a bit after removing the strut? But in another pic, the bolt is removed.
So apparently you were able to remove one bolt but not the other, and thus needed to cut the strut. In any case, it looks like the bushing and it's metal sleeves on both sides is still attached, and that's what needs to be removed entirely. So when installing, the mounting bolt goes through the pre-installed bushing and sleeve of the new strut and attaches to the "adapter" which in turn is screwed into the knuckle.
Sooooo, on the side where there is no mounting bolt now installed, try tapping on the seized bushing/sleeve with a hammer as the metal sleeve is probably seized to the adapter. Not too hard though cuz you don't want that adapter to break off.
As a precaution, try pushing a pencil into the open end of that seized sleeve to check if the bolt broke off when removing it. The pencil should go in enough to reach the outer edge of the adapter. When you are sure there is no remaining bolt piece, use a Dremel to cut the sleeve off "at the outer edge of the adapter nut" assuming you weren't successful with the hammer.
The reason you don't want to cut through a seized bolt is so that you still have something to grip when you finally get the sleeve off from around it. This of course assumes the head broke off the bolt.
If on the other side of the car the bolt is seized inside the adapter, with the sleeve also seized around the bolt, then carefully Dremel off the sleeve WITHOUT cutting into the bolt or adapter nut.
As for the sleeve not being centered in the new struts, I am assuming that is by design to create some clearance. However, you should check the instructions to determine if the protruding side is suppose to flush against the adapter plug, or turned around instead.