I can only relate my experiences of moving my mother.
First, she moved directly from hospital (the US version of sectioning for 10 days) to a care home near me, 100 miles from where she had been living alone. That move was difficult, to say the least. She was in the "assisted living" section of a care home that also has a dementia ward/memory care unit.
Then about a year and a half later, we moved her to the dementia ward, on the advice of the staff at the care home, and also prompted by a safeguarding incident. The staff went out of their way to make the move as smooth as possible and concocted a great story about her other room being flooded due to a broken water pipe. We effected the transfer of her furniture and clothing and so on, while she was out of the facility, so that she came back to the new room all set up for her.
To my surprise, she accepted this right away and never asked me about her previous room, her other belongings, or mentioned the move at all. Looking back, she was farther along than I thought, or wanted to think, and likely couldn't really understand.
It helped that the care home arranged for her best friend to move at the same time, and to the room next door. Again, looking back, she really benefited from being placed in the dementia unit as the smaller rooms, open floor plan, and increased staff and structure were what she needed.
I would say that she was somewhere in the middle to the end of the middle stage when we moved her to the dementia unit, as she is now somewhere towards the beginning of late stage. She is still verbal, but often not communicating clearly, and is completely disoriented to time and place most of the time.
I don't feel that either move caused a downturn of any sort, or increased confusion beyond what was already present. My mother's health improved significantly when she first moved into her care home, as she wasn't safe at home alone and wasn't able to take care of herself.
I don't recall the particulars of your situation, but if you need to undertake a move to obtain the right level of care, or the right kind of care, or the right situation or location, those are all good reasons. I don't mean it should be undertaken lightly, but we do what we have to do.
A quote I like from the US Alzheimer's message board is "care needs drive the decision making." I am sorry I cannot credit the author, but it's a good reminder that we often have to make the choices for what the person with dementia needs, and not what any of us want, or would have wanted. Also, it can work out. Very minor niggles aside, I've been extremely happy with the care home and the care my mother receives. My only regret is not moving her there sooner.
Hope you're able to work it out and best wishes.