I think in the last few posts we're getting to the essence of what 'tightness' is.
Rehearsing is one way a set of players gets tight but mega live gigs with the same core folk really makes for communications and the ability to anticipate others playing.
Thrown together things, no matter the level of players, rarely works as a unit.
Careful! Talking like that, you're gonna run afoul of that crewe over on the Band Management sub-board who take pride in the fact they "never rehearse" and play with at least six or nine different bands…
(And btw…I agree with you completely.