I think some historical background is necessary here. Nowadays IBM isn't a monopoly but during the 20th century, IBM was more or less a monopoly. IBM's antitrust problems go back to their 1936 consent decree and 1956 consent decree. IBM was subject to a huge antitrust case that went on from 1969 to 1982 as well as many other antitrust lawsuits.
The first point is that of course IBM and other at-risk companies will have training to keep people from writing things that will cause antitrust problems. (Their antitrust case had 30 million pages of discovery.)
Second, antitrust cases hinge on the "market" (as a legal term), so it's not surprising that Google wants employees to avoid using that word. In an antitrust case, each side will argue over what is "the market", and you don't want to lose the case because of a random email discussing the "market". Google's recommendation to say "Area" instead of "Market" hardly limits thought, but it makes a big different in antitrust.
Third, I don't want to go all CLS, but antitrust law is pretty much incoherent and illogical. Even after the antitrust case against IBM ended (by fizzling out after 13 years), nobody agrees on whether IBM was violating antitrust laws or not.