This is a hand from Douglas Bridge Club (21 April, Board 17).
North South are playing a 1NT as "12-14, may be good 11". We play normal Stayman, guaranteeing at least one 4 card major. It is either weak (in which case happy to play in either major) or invitational strength upwards.
West's double of Stayman shows clubs
South, with an invitational-strength hand bid 2♠ mainly because of worry about the Club suit for no-trump purposes. North had a minimum opener and passed 2♠, which just made.
The board was played 5 times. At the other four tables one pair stopped in 3♠ (minus 1) and the remaining three bid on to 4♠ (minus 2).
Once you take on board that the 2♠ bid means "I have four Spades and 11-12 points", there is an advantage in opener preferring 2♥ to 2♠ over Stayman with 4-4 in the Majors (if opener chooses 2♠ that forces partner with invitational values and four Hearts to bid 2NT).
The idea of bidding 2♠ on the South hand instead of 2NT was new to me. Then I looked at the EBU magazine from February. It's on page six. Hand 1. In the beginner's quiz. You live and learn...
The author of the article Sara Bell put it thus: "The idea of bidding 2♠ rather than 2NT is that partner can pass if they have a minimum hand with spade support and you get to play in your fit at a nice low level."
[Footnote: If you play a 15-17 no-trump where an invitational hand is about 8-9 hcp, this is more likely to wrong-side the contract. Playing 12-14 the hands are so close in strength it doesn't matter. There are also alternative uses for the 2♠ bid in some methods]