I think you are severely underestimating the technical expertise of the "average customer" here. A large majority of the people who are buying the old games on GOG are very technically inclined gamers who are well informed about what is and isn't in some of these games. If they weren't, topics like this would not come up as often as they do.
While I agree that the amount of people tinkering with the game files is probably comparably high among GOG users (compared to say Steam users) I think you are overestimating the technical expertise of the actual "average customer". There's millions of accounts here (I think GOG stated something about 1.4 million customers being served each month). The active forum members are more likely to care more about that kind of stuff but they pose only a fracture of all the GOG users out there.
Perhaps I am overestimating, but the fact is, if they did include the "broken" stuff in every release, we would have just as many posts about "feature X is broken" as we already have posts about "feature X is missing", if not many, many
more (because people would be actively trying to fix the broken stuff and seeking help from the community). Even if it is only the more active forum members posting about it, there are far more non-active members and others reading
about it, and that is bad press that GOG does not need. Not to mention, information about what is broken would very likely work its way into the reviews of the games, which again is bad press GOG does not need. It is safer for them to simply not include that stuff they can't get working.
However, let me be clear, I am only speaking in general here, not about this particular release. In the absence of more information from GOG themselves, it does appear that this missing content was not done for the sake of a "clean" release, but rather to either meet a deadline or out of some kind of laziness. I didn't even buy the Larry stuff and that kind of pisses me off.