The point with a Shorai charger is to charge each cell to its full potential. Generic chargers can't do that. Except on Earth-X (IIRC) which has the balancing function built in.
Unless the world has evolved since I read "all about it".....
You are correct.
For those who ride infrequently, an AGM battery has a self discharge rate of about 20% a month. An LiFePO4 has a self discharge rate of 3%. You do want to charge before it gets below 13.4 volts though.