[noAnswer]

> but is there a value proposition?

Straight from their FAQ: We see emFile customers asking for solutions for bigger files. Implementing exFAT is not an option for us, as it is patent encumbered. SEGGER would need Microsoft's permission to implement and offer it, and our customers need to deal with Microsoft again to be able to use it in their products. This can be time-consuming and also expensive. We feel there should be a free alternative. The more popular BigFAT becomes, the better.

I guess using anything but FAT would make it hard for their developer base.