Yeah, in fact that goes both ways.
Some books undergo revisions without acknowledging it. They might have some extra pages tacked on in back, or there might be some manual changes to a plate or two, but maybe they don’t want to mess with the design of the existing copyright page or they just can’t be bothered by details. It’s also not that uncommon in older books to drop the copyright date entirely—as above or as on the Ronrico booklets—sometimes by simply removing the year from the existing plate.
One example is the original Savoy Cocktail Book, which has two primary editions before it was completely redesigned: the 1930 and the 1933 “new and expanded”. But there was a reprint in 1930 and two reprints in 1931 and some changes were made during those reprints that were not acknowledged: the year 1930 on the title page remained the only date. The first change—which may have only lasted through one reprint—is that they tipped in a strip of paper with the Bacardi Cocktail on it. We also have a strange interim specimen that has an extra appended page of additional recipes that’s almost a rough draft for the 1933 edition. The 1933 edition is just the 1930 edition with a new cover design, an actual list of printings and edition dates added to the back of the dedication page, and six pages appended at the back with additional recipes (including that Bacardi Cocktail recipe). Given the complexity of the Savoy’s layout, it’s no wonder that nobody was keen to redo it just to integrate 27 more recipes into the flow. Indeed, the title page was only modified to strip the “1930” from the bottom (an additional “1930” survives in the unchanged triangular block of text)
Meanwhile, other books are explicitly editioned without any substantive changes, which is a pain, because you waste time comparing them and can’t find anything. For example, this sort of happened with Ted Saucier’s book: there are in fact only two distinct editions, content wise, but other changes were made across different printings.
Another annoying variant are the ones that are editioned, but without specifying years! Harry’s ABC of Mixing Cocktails is a particularly maddening example. It went through at least fourteen editions, almost all of which have changes, only some of which are numbered, and there are at least five of which we still don’t know the exact year for!