Ok I am going to throw something out there...
G3.5s are, no matter what way you look at it, unpopular with collectors. However, we don't know that they were a complete flop as a line. I have recently started to wonder if the concept of a core 7 characters such as we saw in G3.5 and the end of G3, was in fact successful as a concept. Why do I think that? Because that's what G4 has clearly become. Yes, there is the odd additional character thrown in here and there but in general the line [outside blind bags] are dominated by 6 [plus the 2 princesses] toys.
Hasbro had the model of G3 and it's multitude of characters less than a decade ago. They had the model of G3.5 and it's limited characters. If the latter was truly a completely flop...why stick to the same business model within the line?
Just a thought....