It's nothing to do with your (or mine) interpretation. It is about what the rule states. BA rules state that lounge access (the real topic of this thread) is for gold card holders and one guest. Even if T5 was the only place in the world where they would actually apply the rule (which I strongly deny is the fact), that does not change the rule as it is written.

You can argue that in your view that rule is not good, that you do not like it, that it is not competitive, or even claim as you do that it is not applied elsewhere (which I and other, again, disagree with), but none of that changes the simple objective fact of what the rule actual is.