No, this is opinion. There is no rule that says members of the combiner team MUST all be the same size. What matters is that the size matches up when they combine, and in this case they do. I actually like that there is some variation in heights, and find their scale to the rest of my MP bots to be just fine. To me (and others) combiner bots should be bigger because when they combine they have to form a giant robot. But again, that’s (my) opinion.