I remember testing this out.
Exported database, cleared Simplex of all data so all contacts and convo's were gone. Then had no issues importing the zip to restore to its previous state. I don't know why it's grayed out for you. 

 ah :/ hmm oke thanks fer sharing at least  

 Second this, had no issues whatsoever 

 maybe it's my phone then.. sucks

waiting for simplex reaction maybe they know