I'm not sure I agree with that website, especially given that it is written by a company that only sells lithium batteries. Lead acid batteries, just like lithiums, can be configured many different ways. Where two batteries have the same physical dimensions, the lithium can be discharged more quickly. But at the same price point the much larger lead battery can pump out the same energy just as fast. "Discharge period" is a matter for vehicles, a use case where you want to maximize available power/weight. But on a grid it is reasonable to run batteries that never fully discharge, that never go below say 50% of their total capacity.

For me, the biggest selling point for lead acid remains that the technology is beyond IP issues. I am suspicious of any statement by manufacturers that tout proprietary tech over older publicly-available solutions.