Because frankly, what Wikipedia-- which
anyone can edit - says is no more authoritative than me or you or anyone else saying so. There's no need for a source on whether or not a thinktank leans a certain way. All that's needed is basic media comprehension.
You then insisted I provide a source. So I pointed out that Wikipedia said the same thing about the thinktank you cited yourself. And then (the cherry on top!) you
complained that I DID provide a source, calling it an "appeal to authority"!
Oh, and by the way, your own words:
Literally the only anti-unrealised gains tax argument you've cited from your thinktank was the notion that US citizens would be disadvantaged. Which isn't even true.