Finally we've made the media and now just for interest Digital Spy are now reporting the issue with the promise that it will be addressed.
In the meantime I found a workaround for scrolling/item selection that's working on my controls on Xbox Series S.
When in Buy menu, I use my arrows to select the section I want, it's then allowing me to keep using them in the section too, but I can't leave the section. I have to stay in it and just finish placing what I want from that section. The second I leave the section I lose the ability to use arrows/stick. As long as I keep using the arrows/stick without stopping I don't have to grab the scroll bar or use the pointer. I hope that makes sense. I managed to use buy mode for quite a while without using the pointer to scroll and it was a huge relief. If it's not working I just keep trying different sections until the arrow/stick function comes back, because it's random.
But I also found new problems. Resizing a pool at ground level next to a house with a deck causes a deck height frame around the pool. You can't use it as the pool remains ground height. So it's not even an above ground pool. The frame is higher than the water. It was insisting it had to remain the same Medium size like the first floor of the house, even though it was underground. It wouldn't let me change the pool to Short without this weird deck outline around it. I corrected the pool but I did save the lot to the Gallery called "Canyon View Ranch". It has never happened before.
Also, I've got vanishing items. I buy something, like for example I added planters and window boxes...they kept disappearing.
Edit: I managed to get an image of items becoming invisible as I'm moving or placing them. This was from copying and placing doors. Sometimes it happens after I've finished placing something too.