So chatting with Emily, I've come to understand the problem as follows.
Street Photography is a duplicate of the older Street-Style Portrait Photography. In essence, there is no real uniqueness that properly demarcates the two.
BUT the older niche has an unclear description, and trying to change that description once you buy it may well be rejected because once clearly described, it will be far more apparent that it is essentially the same as the newer, better described Street Photography niche.
@Emily Barnett's partner wants to buy a niche that covers this ground, but which niche should he buy?
If he buys the older niche with the bad description, how will the Tribunal rule on his attempts to improve the description? If they accept them, then the more recent Street Photography niche becomes redundant and they have to reject that niche.
If @Emily Barnett's partner buys the more recent, well defined Street Photography niche, then he is in danger of it being deemed redundant and killed off, because the more poorly defined Street-Style Portrait Photography has seniority (was approved first).