As usual, it's important to emphasize that this research is about therapy, with MDMA as an additional modulator on top of the therapy. In this case, 15 therapy sessions over a period of 7 weeks. MDMA was only involved in 2 of the 15 sessions. If I'm reading the paper correctly, patients received 3 therapy sessions before MDMA was introduced and the bulk of reported improvements happened prior to MDMA being added. Looking at the graphs, there aren't any obvious score increases around the MDMA sessions. In fact, I couldn't tell when the MDMA was introduced without reading the methodology section.
The study was also limited to 6 couples, with no control group. Note that the control group in this case doesn't have to be a placebo group, because it's too obvious if someone has taken a powerful drug. Instead, the control group would simply receive therapy without MDMA and results would be compared. The difference would begin to show the benefit of therapy+MDMA over therapy alone, which is critically important in these trials. You can't just give people 15 therapy sessions and then attribute the benefits to 2 doses of MDMA.
People tend to see these headlines and assume that the drug is doing all the work, or that they can simply replicate the results by taking the drug and seeing what happens. This is usually backed up by a couple of random positive anecdotes in the comment section while anyone with negative experiences is downvoted or dismissed.
Please don't assume you can replicate these results with ad-hoc experimentation with street drugs. If you browse Reddit, it's not hard to find anecdotes from people who have mistaken the short-term effects of these drugs for long-term healing, which usually results in them reaching out for more drugs the next time they have problems. Once people convince themselves that the drug is the easy solution to their problems, they're on their way to low-level addiction.