Where in the 40 books of the 5th edition canon are stats for a Phoenix?
O Seeker of Knowledge, frustrated by a lack of index, go you to The Cradle & The Crescent, p. 106, inset Falconry in Arabia under "Anqa" (because where else would it be?). I do not find stats for this creature, although the text refers you to the Ruhk, with no page reference; it's on p. 176-177, with stats; I would suspect the Anqa Phoenix is not quite so large.
I am surprised to not find a reference to the Bekku bird in Land of the Nile, essentially the same bird, but I don't.
The phoenix is such a legendary bird it was able to ask the line editor to redact details. Neither the phoenix, nor the bennu, nor the bekku, nor the russian Firebird, are firmly given stats or too many facts that might nail it down. It is largely left to the imagination, although such creatures must have bred with humans for the Mythic Blood:Phoenix given in HoH:MC to exist.