Well, given how they handled exporting some Dreamcast games to PC (IE Sonic Adventure being a mess), it's understandable the struggles of porting them to handheld or emulator.
For example, they could make the PC version of Sonic Adventure a game fixed into a handheld device and we wouldn't be able to fix it.
Yeah, porting is tricky. I remember two SEGA Saturn games (Cotton 2 and Cotton Boomerang) which were ported to modern system got many critique since they have 10 or so frames of lag between input (it may not noticable for non shmups fans). Some genres may handle a little input lag better than others, but shmups certainly aren't one of them.