In a similar confusing fashion I posted this about PSN and 505 (GoW)
Despite games like Warframe doing this type of “discount” 505 seemed very much disinterested in adopting a similar policy so I don’t know how "hard’ or if they tried at all to get codes (my guess is they brought it up - PS said it would be difficult they said np next topic) 
Back to the OP however; The no free DLC on PS4 I don’t buy as I have downloaded free items on games like The Division and others in the past. It may be some “hoops” to jump through to get them on the PS4 but it can be done as other publishers have done it and are still doing it (Battlefront, Batman and many others all have done redeemable codes for free in game items / DLC ).
For another example of how to do this look at Borderlands they’ve had zero issue getting redeemable codes for DLC to PS4 and Xbox for as long as I can remember- the last one was a few days ago for BL2 and the Pre-sequel. They push them out on Twitter frequently! Why can’t 505 do the same on their twitch stream, Facebook or twitter…?
I just don’t think there is a “will” thus there is no “way”