My point is that this is not an isolated incident - official or not.
To me it's more of a cultural attitude. Ask any Scottish tennis fan and they'll tell you that Andy Murray is British when he wins and Scottish when he loses.
Imagine if an organiser in Scotland started calling things `British Knockout...', or 'British Championships...' followed by making zero effort to involve other nations and at times actively discouraging them. It would be completely absurd! To repeatedly falsely name tournaments in this way comes across as arrogant and entitled - this is the crux of the matter.
Btw, I sympathise with your ageism claims. This British knockout has clearly changed to a youth vs stars tournament. Check out the list of sponsors and they are nearly all from junior chess sources. Also chuck in the organiser's kid for good measure

Regarding Rowson, I only recall him being drafted in once as a last minute replacement, but I could be wrong.