Inverted Use of Two-Under?

An auction discussed a while ago between friends just occurred to me as offering an interesting use of two-under bidding.

Opener started with One Spade.  Responder bid a forcing 1NT, and then Opener's RHO intervened with a nuisance Three Clubs.  Opener then bid Three Hearts, to Responder.

1S-(P)-1NT!-(3C)
3H-(P)-?

4C was agreed to be the "expert call" of choice-of-games, possibly with 2S/3H.  That meaning, however, deprives the partnership of a cue-raise to suggest slam interest.  One alternative would be for 4C to be a heart flag and slammish, 4D a spade flag and slammish.  But, that forfeits the choice option.

Two-under bidding allows both meaning to be employed.

Responder would bid 4C as "one or both majors," meaning (1) a cimple raise to 4H, (2) a simple raise to 4S, or (3) a choice hand.  Opener indicates choice, bidding 4D with spade choice.  After choice is indicated, Responder bids 4H or 4S.  If he needed choice indicated, he bids the major Opener selected.  If he did not, he bids whatever major he intended all along.

With slam interest, instead, Responder can bid the major directly.  Hence, an immediate 4H or 4S would be a slam move in the indicated major.

4D would be natural.  Or, 4D could be a "choice, and slammish" call.

Thus:

1S-(P)-1NT!-(3C)
3H-(P)-4C-(P)
4D(spade preference)-(P)-4H = just hearts

1S-(P)-1NT!-(3C)
3H-(P)-4C-(P)
4D(spade preference)-(P)-4S = just spades or needed choice made

1S-(P)-1NT!-(3C)
3H-(P)-4C-(P)
4H(heart preference)-(P)-P = just hearts or needed choice made

1S-(P)-1NT!-(3C)
3H-(P)-4C-(P)
4H(heart preference)-(P)-4S = just spades

1S-(P)-1NT!-(3C)
3H-(P)-4H = heart fit, slammish

1S-(P)-1NT!-(3C)
3H-(P)-4S = spade fit, slammish

1S-(P)-1NT!-(3C)
3H-(P)-4D = diamonds (option 1) or choice-and-slammish (option 2), depending on partnership agreement