Fast arrival should be used to discourage partner to go on.
I would never expect this control monster.
Yes i know it should be save to bid 5, but don't lie to yourselfs! You don't bid 5 every time you think its save! You bid "save 5" after you notice that 6 are unsave.
Tell me you never played with or against someone you opened 5♣-5♠ with 1♣.
what about:
or even
I've seen worse hands jump to game at BBO, Vuln. @ IMPs 40% chances should be taken to game.
These are all impossible, or infrequent? But this "monster" is frequent?
The question was, who should go for slam.
South bid shows values including distribution good enough for a game try. There are lots of distributional hands, that qualify for that, the frequency of that "monster" is rather rare. Bidding 4♠ may be a "system conform" bid, but it does not describe it's true power. Fast arrival may not be part of the system.
Does the north hand look promissing, no it does not. Partner opened ♣ , meaning that his ♦ are 3 cards at most, his QT is a big hole to fill on the way to a slam.
North has a good share of responsibility for missing the slam, but south could bid more helpful, and if not the system needs some improvement.

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