Kishi wants to show Madara's vast arsenal and superiority, that he can deal with situations using numerous ways. Also preta path is more suited on defending against ninjutsu because it casts a barrier around the user unlike the absorption jutsu that needs physical contact before it can absorb. Also I think the absorption jutsu doesn't come from Hashirama Dna, else Hashirama would have commented on it. Also Hashirama have not showed the ability to absorb ninjutsu with physical contact, only his Mokuton showed that ability. The absorption jutsu is more likely the same jutsu Yoroi, Jirobo, Kisame, and Orochimaru used, only Madara showed better mastery among them which is not really a surprising on a shinobi of his caliber. Lastly, Hashi said Madara regained his past ability, implying Madara had the ability during their era.