They probably did a bunch of songs together. U gotta keep in mind that RZA always has the final say in who makes the final cut of a song.
Examples: "Wu-Gambinos" from Cuban Linx originally had Inspectah Deck on it.
"Ice Water" from Cuban Linx originally had U-God on it but RZA cut him off.
"Verbal Interourse" from Cuban Linx had an extra Nas verse.
"Meth vs. Chef" from Tical had another Method Man verse.
"Supa Ninjaz" from The Pillage originally had Ol' Dirty on it.
"Wu-Tang Aint Nuthin To Fuck Wit" originally had Ghostface Killah on it.
Ya get my drift.