Actually, you're right. I looked it up. I was under the mistaken impression that I had read somewhere that Lynch wanted to shore up the interior line against the run. But all the stories quote him saying the opposite, that they wanted to get Hargrave for his pass rush ability because he felt the pass rush disappeared for the 49ers in their last 3 games.
Hard to believe that you need to shore up the pass rush when you have Nick Bosa (18.5 sacks, 19 TFLs and 48 QB hits!!). And I wonder if it makes sense to move on from Omenihu and Ebukam if you are concerned about the pass rush. Ebukam had 5 sacks, 7 TFLs, and 13 QB hits. Omenihu had 4.5 sacks, 3 TFLs and 16 QB hits. Hargrave had 11 sacks and 16 QB hits, but played 200 more snaps than Omenihu or Ebukam.