As much as I love my 5 completed Hasegawa fighter mode display models (VF-0S, VF-0D, VF-22, YF-19 & SV-51), I'd have to agree that the proportions don't always follow the lineart 100%.
The Hasegawa VF-0D, VF-0S and SV-51 are probably the most accurate, but the YF-19 & VF-22 are far too slim when viewed from the side IMO. The same would also apply to the VF-19A and YF-21, which are basically the same kits. I still love them though.
I personally have no interest in seeing variable models from Hasegawa. My experience with variable plastic and resin kits from Imai, Bandai and SHE over the last 2 decades has led me to the conclusion that they are just too fragile and have too many compromises to be worthwhile.
My mindset is if I want something that transforms, I'll buy a toy, I want something purely to display, I'll buy a non-transforming model.
Graham