* What you are asking is 1) if I dilute sorbate below recommended dosage level will it still be active? 2) are there live yeast in the treated wine?
* the K sorbate will lose functionality if it is not at the appropriate treatment level. We know that it naturally decays with time so the active chemical is reduced. You are also diluting so the active chemical is again reduced.
ie mixing creates a risk factor, if the yeast is still active it could restart and is not recommended
* yeast will naturally die with time and other stressors as sulphite and alcohol. If you have a significant time the yeast are dead! , ,
I like to age 9 plus months and not use sorbate. Normally it works. BUT sometimes not. If you have minimal time as a week the references suggest that yeast is still alive but not reproducing. From back sweetening dry wine I expect live yeast to still be lurking at 3 months. At 6 months I would give it a 50% probability, ie it referments enough that I don’t do it.
Your risk is a few gallons therefore low. As
@NorCal says probably zero if the treated wine has been there a month.
In a food plant situation I would never do it since every extra gallons magnifies the risk.