Hybrid Madness Lesson Question

I've just stumbled upon your Hybrid Madness lesson and was curious when using your middle and ring finger to do the picking, I felt like it would be easier to use your middle finger after the second downstroke with the pick. For example, in the first riff, the first time you play the D on the 7th fret with the ring finger, wouldn't it be easier to use your middle finger since your hand moves down a string to play the down and upstroke around that D on the 7th fret? Sorry if this is confusing. If there is an advantage to using your ring finger there I'd like to know so I don't create a bad habit using my middle finger when I shouldn't! Thanks