Short answer: it is not established that combining MDMA and psilocybin treats anxiety or depression. Evidence on the combination is very limited, and most rigorous research has evaluated each substance separately in controlled settings. I cannot verify claims of unique synergy or superior outcomes.
Some people report that the mix can feel emotionally supportive while encouraging deep reflection, but effects vary, and combining substances can increase risks. Potential issues include acute anxiety, elevated heart rate and blood pressure, overheating, and dangerous interactions with medications such as SSRIs or MAOIs. The combination is not an approved treatment, and legality is restrictive in many places.
If you want a balanced overview, see this Q&A: discussion of “hippie flip” in a therapeutic context. Any consideration should stay within regulated clinical research with qualified professionals; avoid self-experimentation.
Bottom line: potential benefits are unproven, and safety and legal concerns should come first.