With 5♠4♦ hands, no matter how strong there is no real need for bidding 2♦, you know of 8 spade fit. So it more logical to use it for 5♦4♠, now with this distribution and GF you will begin with 2♦ over 1♠, so it cant be GF, it also cant be too weak since you would have bid 2S, so it should be somewhere in between and should therefore be constructive but not forcing.