The point is what mismatched batteries with different internal resistance do.
The one with the lowest IR does the heavy lifting, provides more of the load.
If it is in parallel with a
battery with double the IR, that one will give two thirds of the current.
After the load eases, they will balance each other.
Conversely, the low resistance
battery will charge fastest but afterwards they will balance out.
This is not just theory. I have big AGM batteries wired in parallel with a 100Ah Lithium, and separate ammeters on them. I see this happening.
Ir works well for me, and has done for several years.