That is definitely part of the blame. Every company has done Motormaster slightly differently, and every time it's been a huge clusterfuck because they just cannot give up the idea of trying to make the trailer be part of him/the combiner in multiple ways. I think thats what trips everyone up.
Meanwhile Devastator they've made a perfect Legends sized version that has 0 partsforming with good individual robot modes. The only downside of the whole thing is the individual 'bots don't have neck articulation, which at that point was just the company cheaping out, they could've easily fit them onto the figures.