Here's a quick test. This battery also goes down to 11V briefly when cranking.
Depending on which source you believe 13.15V for 4 cells is around 50% to 60% state of charge. Probably equivalent to a Lead Acid battery at 12.2V to 12.25V
Not bad for a tiny 30Ah battery?
https://youtu.be/9tn8EEt0uWQ