It means batteries are different. Take two boxes of chocolate cupcake mix dump it in a huge bowl then mound it into a tremendous lump on a baking sheet. No matter how much the cupcake batter company yells and twists arms...
It ain't a brownie...
And just because a lowly group 24 battery has the same cranking amperage as a pair of GC220 batteries it means the group 24 will start a car the same as the golf car batteries...bit inversely you may not make it to the 2nd hole with the car battery.
BFL13's didn't act like a completely different type of battery. Why? That's in the explanation...