Not sure where that info was seen, but 100% not true.
Phoenix have never been used in American ohiki by proper breeders at least. Some cons mixed everything they could but they are gone now.
The two are too far apart type wise for it to work in any kind of benifical way. The UK did it and thats why they have hard tailed, narrow bodied, long leg birds.
Bantam phoenix have been here for decades. Ohiki were only imported in 2002 by my buddy.
She is the one who made all the new colors. Cochin, english orps, and wyandotts were what was used.
Bantam phoenix were made over 100 years ago off dutch, old english, and various game type birds that were similar is size and shape.
Since the tail genes are dominate it was an easy cross with similar body types breeds.
But no, in the US the ohiki and phoenix have not been used in any kind of orgainsed breeding.