You're right of course. My frustration is that I've been waiting to return to true white sleeves since Puma took over, and because every one of Puma's templates have always connected to the collar, they just paint fill their latest template into "Eh, that's close enough for Arsenal" range.
It was fine and understandable for the first year or two of the Puma contract (and I'm not opposed to mixing things up like Barca does), but now that Puma is scrambling to differentiate their kits from their past 3-4 offerings, they never make the obvious change. Last year was "What if we did a sash/stripe on the front?" and this year is "What if we did a slightly darker red and have a collar?" while the obvious answer is to actually make a true Arsenal shirt for once.
And yes, they might need to modify a template to actually make it work, but when you're Puma's flagship team, they can work with or around your needs.