What goes down on the record books is still the number of times he coached a team to win the gold. Not the number of assistants that became good in the same field. He had no control whatsoever on that so why take it against the guy.
But stats, rings and records dont always tell the complete story - if it does, then Robert Horry, is a greater player than Michael Jordan ....... or a guy with rings, like Joel Anthony, being greater than those with zero rings, like Malone, Barkley, Ewing, etc.
IMO a head coach entails many functions; among others, you're a tactician, motivator & a teacher as well.
Phil Jackson has had many contemporaries, who had also coached in the NBA for a looooong time ...... yet most of these contemporaries, like Riley, Popovich, Brown, etc has spawned very many successful head coaches, bearing the same or similar coaching styles and have won championships, contended or at the very least, had winning records.
Phil Jackson also had his share longtime assistants who went on to coach their own teams - yet not one of them turned out a winning record and not one of them showed a working triangle offense ....... anyone can watch a handful of KNICKS games and see the clumsy mess that D. Fisher calls his triangle offense.
There's a quote, "if you have knowledge, let others light their candles with it" ...... it's very likely that Phil Jackson shared his with his many assistants - yet no positive results from any of them (count D.Fisher and Lindsey Hunter on that failure tree as well).