What exactly is the KCOM catchment area?

I've been trying to get an accurate map of the KCOM catchment area (to determine whether a house I want to buy is unfortunate enough to fall within it), and I've discovered something odd: it seems to be up for debate.

The only map I've come across that seems to be really accurate is this one taken from the 'new wholesale services request' PDF from KCOM:
KCOM catchment area

However, this appears to be less of a "KCOM map" and more of an "exclusively KCOM map", because on their site, KCOM provide a map claiming coverage of this much wider region.

Testing with KCOM's and Zen's (BT network-based) availability checkers seems to suggest that areas in the former blue map are KCOM-only, with no BT service, and some areas outside of that but within the latter map (such as addresses in Market Weighton) can actually get services from either. Is this true?

By the way, I also have a secondary question: my understanding is that KCOM are subject to LLU requirements in the same way that BT are. Why don't third-party providers like Zen use this to offer their services in the KCOM-only catchment area? Is it price, or some technical reason?

Why do you not contact them and ask ?.
I used to have Kcom in South-Derbyshire via Openreach and My daughter used Kcom in Essex !.
I presume you are just talking about the Hull area only.

The first map covers the area where they are the incumbent provider, so no Openreach-based services available.

To answer your secondary question, they provide wholesale access in much the same way as Openreach do for FTTC & FTTP, the communications providers may not consider using it to be worthwhile commercially. I'm not sure if they offer any traditional LLU, somewhat moot as they are withdrawing all copper services next spring https://www.ispreview.co.uk/index.php/2022/07/hull-u...

Since completing the FTTP rollout within their licensed geographical area they are building networks beyond that, in this respect they are no different to any other alt-net operators.

They have provided internet access over Openreach infrastructure elsewhere in the country having purchased Eclipse Internet back in 2005.