I will rejig my test lab tonight and give it a go:
I will try a normal word and an alphanumeric combination.
At first glance it does look like the Rainbow tables we all know but this could be a handy resource for testing home .cap but like mentioned previously i wouldnt utilise a service like this for a contract pen test. I would inform the company of this service if the SSID/pass could have been cracked by the aforementioned rainbow tables - just to highlight insecurity's to them.
Ill report back later on with my findings