Sounds like trying to decide whether lower-calorie juice can be...

Sounds like trying to decide whether lower-calorie juice can be just as nutritious if you drink it through a wider straw. Here is how E3's website defines it:

Flow Rate: The flow rate ratio is a measure of the rate at which the lithium can be extracted from the brine within a fixed capacity. The higher the ratio, the smaller the DLE commercial plant required, which is a proxy for the capital costs of this system.

https://www.businesswire.com/news/home/20230614600424/en/E3-Lithium-Outlines-Key-Performance-Indicators-and-Provides-Field-Pilot-Plant-and-Corporate-Update

And they say a ratio of 3 or higher, is the standard. And you say that AZL claims its rate is high, without providing any numbers (of course).