I too assumed you are just using the Stenner for convenience and it would not change any of the FC/CYA recommendations.
Would be interesting if that's not the case.
Purely speculating here, but perhaps the reasoning could be that with a single addition of chlorine once a day you need to account for the sun breaking down some percentage of the chlorine before the next dose and therefore need higher amounts to avoid dropping to zero. If you are instead injecting regularly throughout the day perhaps you could have lower overall FC without the risk of dropping to zero since there is a regular infusion?
I don't see how higher CYA would play into it though - if anything I'd guess you'd use lower CYA in that scenario. Again, just thinking out loud, I don't know this to be the case.