I see it as optional. A choice made by the profile manager. If they wish to use "Kingdom of Great Britain" after "Wales", they can.
I wouldn't, but it would not be incorrect for that time frame.
Place, Monmouthshire, Wales, Kingdom of Great Britain OR Place, Ceredigion, Wales. Neither is incorrect. Just as using Sandal Magna, Yorkshire, England for 1899, is not incorrect. There is no requirement to tack on "United Kingdom". Likewise there is no requirement to tack on "Kingdom of Great Britain", just because the date falls between 1536 and 1706.
So long as the "United Kingdom" designation is not used prior to 1801, does it matter if the profile's manager uses "Kingdom of Great Britain" or not?