Well, in a report via Eurogamer, Capcom has explained that his ‘infection’ ability was added to the remake to allow Ganado’s from RE4 to make a little more sense in the overall timeline.

Shooters released since Resident Evil 4 have added progressively more detailed animations to their gun reloads, ... 16 GIFs from RE4 HD. News. By Wes Fenlon published 4 March 2014 ...

Also known as ‘The Chainsaw man’, Dr. Salvador redefined horror for a new generation of fans in Resident Evil 4, and certainly kept veterans of the series on their toes too.

According to Capcom's Resident Evil 3 development team, the Nemesis' ability to infect zombies with parasites in Resistance was added to the game to tie into the Ganado enemies of RE4.