The cod armor is the important part.
The wrist computer (self destruct) and the plasmacaster are considered gear. It’s just not gear we can alter. The lack of the computer and gun means it either wasn’t added to the model for the purposes of the promotional render, or that as far as the presumed Master armor goes, they’re not ready yet. Which would not be the fist time this has happened where our first look at Hunter retained the Jungle Hunter plasmacaster. Or for that matter the City Hunter’s spear being shown in trailers where the game launched with its own rendition. Sometimes it just isn’t ready. And to add, the default armors are put on in parts hence glitches where Predators can occasionally spawn in nude. The cod was just what was on in this case that was otherwise new.
Why show it in this state? To tease the community, and otherwise the important part is the mask. Do you need the gun or the computer to get an idea what the mask will look like on a Predator? It’s a mistake but not one indicative of the whole Master armor which isn’t even the point of the advertisement.