As a preliminary matter, in what contract would you want to play the following hand:
Clearly, the obvious contracts are 7NT and 7♠. Only 5-0 spades defeats 7NT. 7♠ goes down when spades are 5-0 behind the long spades or if there is an opening ruff. If spades are 5-0 in front of the long spades, there may be a coup. And, if spades are 5-0 behind the long spades, 7♠ goes down less than 7NT.
In any case, you want to be in the grand. You would be disappointed to only get to a small slam on these cards.
My friend's teammates were in 6♠. This was a lucky mistake, as the spades were, in fact, 5-0 behind the long spades. They won a swing on the board. Was it because the opps at the other table bid the grand? NO!
At the other table, my friend, who likes to open, shall we say, somewhat light, opened the Txxxx of spades 1♠! How do you get to slam in a suit in which the opponents opened the bidding showing 5? The opps got to 3NT.
Bridge at its finest.