The fear of controller-battery voltage drop is that it will not let the batteries reach the controller's high set point, so the batteries will be undercharged.
If amps have tapered by then, the voltage drop will be less anyway, as Almot mentioned. Regardless of that, you can just raise the high set point to allow for the drop so as to get the batteries up where you want for Vabs.
But that all depends on where the batteries ought to get to. Nobody mentions this. AGMs and Wets not the same and AGMs vary among them. Maybe your set-point is already high enough even with the drop.
And even if not, who cares about that if your bank is so large compared with the size of your solar array that you will not get it full by dark anyway? Solar then is just a help to reduce your gen time. Nothing wrong with that either, but it means you don't care about the finer points of reaching "full" or being "undercharged" from the solar.
That is another of the many possible individual situations where only you know what you really need. All we can do is say how ours is working and you can decide if that has any application to your own situation.
