Simply, the sample size is tiny and far less than that required to give a sensible answer, only 20. It's also worth taking a slightly critical look at the organisation promoting this, the Multi-disciplinary Association for Psychedelic research, who specialise in researching banned substances. They've done quite a lot of work on LSD (somewhat unsurprisingly, given the name).
It's certainly worth more consideration and research and I take their point about MDMA allowing people to open up, that is after all what made Ecstacy so popular in the first place. However I won't shout it as a wonder cure just yet.
I've had a look at their website. They are planning to carry out research on military veterans, and have applied to the US research authorities to allow this to happen. However there are two fairly major problems with the proposal. Firstly they're only planning to trial this with 16 veterans, meaning it'll have basically no statistical reliability, and more importantly from their point of view "the study will cost $500,000. We still need to raise $475,000". They've already been fund raising for 7 months so it isn't likely to happen soon.