I was reading through my booklet on the tester i have. Your correct also. Says some battery manufactures state that 12.6 volts can be interrupted as fully charged.I've been doing automotive electrical repair for 20+ years. When it comes to lead acid and agm batteries:
12.6 = 100% state of charge (SOC)
12.5 = 75% SOC
12.4 = 50% SOC
12.2 = 25% SOC
Sled batteries are no different.