There are both physical and chemical differences between DEEP CYCLE and Starting or dual purpose batteries.
The result is the recommended minimum SOC for Deep Cycle is 50 %
Where as for others it is 75 to 85%
ALSO.. 2 weeks ago yesterday I went to start my car. NOTHING. NO lights. No sound NO DING DING DING nothing. I jumped it and went to Auto Zone where they dropped in a brand new battery (Warranty no charge) Did not even test it.> WHY. With a STARTING battery you get to do that one time then it's new battery time. And that was the one time.
With my GC-2's (DEEP CYCLE) I took 'em down to "Steps would not move" and "Lights would not light" like 3 or 4 times over 9 years and they recovered. Oh had I not done that they might have gone 10 years. but they recovered