Where did I say that then?
Of course he would not play as a DM.
Fekir would play as a N:o 10, and Keita would drop back.
Then we would be conceding even more than what we did. Keita is more offensive than Henderson. It might work against the weaker teams but we would be less balanced. Fekir was being bought as an AM and we bought Shaqiri instead to rotate with the 2 or 3 AM, not with Henderson
Henderson's natural position isn't as a DM. In Sunderland he used to play as a right mid. He has learned over time to be more defensive than what he used to be. He is really more of a box to box midfielder.
Keita is a player that is as versatile as they come. He can break up play and also be quite offensive.
Klopp doesn't really want to play with specialist players. He wants them to be able to rotate and interchange.
Hence it would make sense to play with for example Fekir instead of Henderson, simply because he would make the starting XI better than what it would be without him, and with Henderson in it. Keita would drop back and be more defensive orientated while Fekir would play as a N:o 10 just behind the front 3.
Whether it will ever happen I don't know, but that is another question.