IMO after
(1♣) _P (1♠) 2N = Red 2-suiter.
(3♠) _P (_P) 3N = Strong 6-6. (X = strong 5-5. 4♦/4♥ = longer suit e.g. 5-6 or 6-5).
(4♠) _P (_P) _X = Strong 6-6 with quick tricks.
With such a strong hand, it makes sense to consult partner about strain because ♦ will often play more than 1 trick better than ♥.
ELyk25 tells us that opponents can make a slam but I think you are likely to win the auction at the 5-level because opponents were willing to stop in a partscore.