This is a situation I have never come across before.
While preparing to defend, after LHO has opened an announced 15-17 1NT, we ask one of our routine questions: "can declarer have a 5-card major?".
"Yes", comes the reply, "but not in spades". And if I recall correctly, the CC was perused at this point to find a note to this effect.
Obviously, situations exist where we would be entitled to this information earlier than at opening lead time. But how/when should this information be made available?
Benefits include:
Plus... it's free!