Ah… I remember when this was all the rage with people.
I don’t know if anyone ever really had any idea whether matching phases or complementary phases matter more. The TikTok trend started telling people that matching phases = twin flames, complementary phases (that form a full moon together) = soulmates, but I don’t know where that came from, and I don’t believe it is ever that easy.
I don’t think anyone who is really on the twin flame journey is going to tell you that you need complementary phases or matching ones. They can help give you an understanding of some of the energies between you in the 3D, at least.
Lunar nodes are way more significant for karmic connections than birth phases. When one person’s planets touch another’s north or south node, that’s considered a major past-life indicator. Also, look at whether you have any 12th house connections in your charts - that’s the house of karmic bonds and unconscious recognition.
The waning crescent specifically is associated with prophetic abilities and completing unfinished business from previous incarnations. If you’re both born under it, you might both be in similar stages of soul development, working on closure and preparing for new cycles. There’s something about that phase that makes people natural healers and guides for others going through transitions.
Three days apart in the lunar cycle puts you in the same 45-degree phase segment. Your emotional processing styles would be nearly identical, which creates instant understanding but can also create friction if you’re both going through the same mood simultaneously. Different phases might actually balance each other out better in some ways.