Seems to be some confusion here. 12s unless true deep cycle like T-1275s have less antimony so they self discharge less than 6s with their higher antimony.
Self discharge is related also to how clean the battery tops are for any battery type.
It would be interesting to have some data whether there is more self-discharge for a pair of T-1275s in parallel than with a pair of 6s in series. I have both types but have no data on that.
12.3 is 60% with some wet batteries not 12.2 which is 50% with some (12.1 is 50% with others). Anyway the usual rule is to stay above 12.4 but then you have to consider which type of battery you have. AGMs have a higher resting voltage than wets eg.
Got to be careful with this stuff in case we confuse a newbie.