The word "zombie" never appears in the game. Instead, the infected are called "freakers, swarmers, newts, breakers, runners" etc.
Days Gone is not Sam Witwer's first zombie-apocalypse related acting role. He also played the zombified soldier that Rick Grimes encounters inside a tank in the premier episode of The Walking Dead TV show. Coincidentally, or perhaps not, the title of the episode is "Days Gone Bye"
While Days Gone was still in development ever since it was first announced in 2016, the earlier versions of it included narrative choices which could change the storyline of the game. For example, as shown in May 2018 gameplay footage, originally in the opening missions of the game there was a choice of either killing Leon or leaving him to Freakers, and either choice would effect Boozer's morale, and later when Boozer gets injured by Rippers there was a choice of taking his shotgun or leaving it with him while Deacon goes to find some medical supplies.
During testing of the game, developers realized how not only that this didn't work and the players didn't get it, but it also wasn't needed. Biggest problems were that not only some choices would make Deacon seem unlikeable, which is not what they wanted for the character, but it would also cause many re-writes and changes needed to keep the original intended storyline to happen as it was written and planned. Entire "choices" feature and all the alternate options were cut out, so in the final game Deacon always makes a good choice, and according to developers, this decision actually made the entire game even better. This could explain why in some cutscenes there is a strange pause between Deacon and characters he is talking to, because it's probably where some of the good or bad choices could have been made.
During testing of the game, developers realized how not only that this didn't work and the players didn't get it, but it also wasn't needed. Biggest problems were that not only some choices would make Deacon seem unlikeable, which is not what they wanted for the character, but it would also cause many re-writes and changes needed to keep the original intended storyline to happen as it was written and planned. Entire "choices" feature and all the alternate options were cut out, so in the final game Deacon always makes a good choice, and according to developers, this decision actually made the entire game even better. This could explain why in some cutscenes there is a strange pause between Deacon and characters he is talking to, because it's probably where some of the good or bad choices could have been made.
As part of a patch, a BB container from Death Stranding (2019) can be put as a tank for Deacon's bike.
Of the various firearms usable in the game, one of them is a lever-action shotgun that can be wielded while driving on your motorcycle. This is more than likely a reference to Terminator 2: Judgment Day, in which Arnold Schwarzenegger drives a motorcycle and uses a lever-action shotgun.