If his details don't match, it doesn't change anything. OP and VS both said that name and DOB were matched, you would need at least two details more or it's 100% irrelevant.
Just keep wondering why OP is making it so complicated because any casino carrying UKGC license know their Gamstop things and honestly don't know casinos who wouldn't send player money same moment when they realize that they fcked up with GS. Then players who find it hard to download and send to casino with my experience are 99.87% of times bit wrong in their claim (op haven't say anything wrong, don't mean that but he only referred to these two details like VS and if not making at least two more, worth of nothing).
Sorry, what two details? Take a look closer on the date he registered to Gamstop and the date it ended. As previously said; VS stated his registration was made in early 2019 and have been active since (their words).
The date when Gamstop ended (05 September 2019) is not an early time of the year, which means he registered before that.
P.S the OP replied to the thread, lets wait and see whats happens!