Which official site? Hacker like the site which A-OK gen on and the author of Pokedex FAQs (TFerguson) say rank does not affect the recruit rate.
From the site which A-OK gen is on
=====================================================
* The recruit chance depends on the species of the defeated Pokemon.
* If the team leader is holding a Friend Bow, add 100 to the recruit chance.
* A number is added to the recruit chance depending on the team leader's level:
o 29 or less: 0
o 30-39: 50
o 40-49: 75
o 50-59: 100
o 60-69: 125
o 70-79: 150
o 80-89: 175
o 90-99: 240
* If a random number from 0 through 999 is less than the recruit chance, the Pokemon can be recruited.
* To be recruited, the Pokemon and the team leader must be within a 1-tile range of each other.
===============================================
From Pokedex FAQs
===============================================
The maximum bonus (L90+ and Friend Ribbon) is 34%. Please note that
Rescue Team Rank, Party Size, Type and so forth cannot increase this
chance, though some factors may contribute in preventing you from
recruiting the Pokemon at this time.
===============================================
« Last edited by nhahtdh on Jul 23rd 2007 »