The issue is that they may or may not be actual MDMA - and the unscrupulous label general amphetamines as either molly or MDMA and people unfamiliar dont know it....
The clinical studies should, presumably, be also, setting a standard for the purity, dosage, quality etc around the tested substance...
So to go "off grid" as it were, to test this has risks..
That being said - the efficacy of any therapy session, even when the introspection and emotional response is deliberately induced, could still result in benefits.
The problem with any drugs, beit alcohol, weed, whatever - is that environment (situational and historically) play a large part in the response.
The mental state can be associative to a great degree, and as such - if one has had a tool such as MDMA in the past - but in a really poor environment, the response could be poor.
Read up on it - but never trust anything off the street to be what they claim...