I think that the first one may also be by the same hand as the third and fourth. Whoever "Bruce" is, he seems to have a printing press of Steinbeck books, and Steinbeck must have been his BFF or neighbor.
Since the second one is clearly not by the same hand, it would appear that "Bruce" may just be signing more than his own name. When have you seen four inscriptions, with a full first, and rather long last name, which would have had to have been spelled out. In the last two, it just has "Bruce" and John's names, with nothing else, another oddity. Personally, reviewing the evidence, I would steer clear of anything with "Bruce's" name on it.
It seems that lucky "Bruce" got multiple copies of the same book signed.
but the second one has the bizarre just two names, without the "for" from your example above.
Looking at some other apparently legitimate booksellers, the Steinbeck signatures are consistent with one another, and not consistent with anything that also has "Bruce's" name on it.