I'm wondering... and this is only just supposition on my part.
Facts
The original WOOSH test was only available to Wholesale based ISPs, and many, many years ago the likes of Sky kicked up a stink because there was no equivalent for LLU diagnostics.
We then went through a silly phase when WOOSH was withdrawn and neither the ISPs nor visiting BT engineers had access to any of the WOOSH data. KBD was then developed for the ISPs and Openreach engineers got W(H)OOSH back.
Supposition.
What was originally WOOSH, got renamed to WHOOSH for Openreach Engineers?
Its only when performed by the ISP that it becomes intrusive? I can guarantee you that when I asked Plusnet to perform that GEA test on my line last year, it definitely made me lose sync.
Also noted is the fact that you said your WHOOSH GEA test gave you some slightly different info as well as to what the ISPs get. I wonder if for the sake of the LLU ISPs that part of the service does have to be disconnected?