Excellent point! But that also raises the question of internal 'dynamics' in NATO, as the organization expands. Forty years ago, would the terms of the treaty have been sufficiently compelling for London and DC to have risked nuclear war, if West Germany was attacked? It's just a guess, but I would say "probably yes".
And today? Will DC actually go "all in" if Estonia is invaded? At a minimum, it's likely that the level of commitment will vary, depending on the administration. A Donald Trump may be a dependable ally for Estonia, but what about someone like Joe Biden? And with overt corruption becoming rampant in American politics, it might be that future NATO actions are essentially determined in Beijing...
;>)
The is why NATO in its current form needs to be changed.
It needs to be broken up into separate interlocking (maybe!) defense alliances. One for Central Europe to Southern Europe, one for the Baltic\Scandanavian region & one for the North Atlantic countries. This takes Europe off the USA defense dole, allows for a more nuanced response if its called for (Like for local problems like the Balkans (Why were we involved other then Clinton Administration wanted to disply their defense chops!) and more freedom of action for member states. This monlithic appraoch draws us into things that aren’t our concern and allows Europe to continue to sponge off us.