Simple explanation...
Sig didn't publish that catalog.
HK didn't publish that infamous catalog, either.
They're not publishing houses, they're gun manufacturers.
They farm that stuff out to companies that actually do that full time. Same with their magazine advertising. And often those companies employe people who aren't as familiar with firearms as, oh, we are.
Obiously Sig has people who have insight into the production, and who approve it, but they don't have people standing over ever step in the process.
When I was associate editor of American Rifleman Magazine back in the early 1990s we interacted quite a bit with representatives of the various companies over placement of advertising.
We virtually never actually talked to an S&W, Colt, Ruger, Browning, etc., employee about that sort of stuff. We talked to the representatives of the advertising firms that S&W, Colt, Ruger, Browning, etc., hired to take care of that for them.
The text error could have crept in at just about any point in the production process, from initial copy to final boards.
The HK photo error? That was screwed from the very start.