All need to be defined
3N can only be a suggestion to play and with a normal 5332 (and even a stopping value in ♦) there is absolutely no reason to bid 4♠
My guess is that after showing a 3-card-support we can never stop in 3N (Might be the same reason after 1Ma-3N, where the bot almost always remove to 4Ma)
Traveller
A direct bid of 3N or bidding 2♣ followed by 3N is the key here, but how can we know 3N is the right contract :-)

Help

