NIC Card Thousand Faced Shadow

Rules Question about the NEO card Thousand Faced Shadow. Their ETB basically triggers if you used the Ninjitsu ability, but why is it written out describing what happens when you Ninjitsu instead of referencing the keyword?FYI its text is: "When Thousand-Faced Shadow enters the battlefield from your hand, if it’s attacking, create a token that’s a copy of another target attacking creature. The token enters the battlefield tapped and attacking." I was think of something like " When ~ enters the battlefield, if its Ninjitsu cost was paid, create a token..."
I know it's not 100% the same since you could trigger the ability in other ways, such as with Ilharg. Or was it intended to work with the few cards that do that instead of the IMHO easier to read text referencing the set mechanic? Or am I missing something entirely, in that case please let me know.
As always thanks for the opportunity to ask questions.

If we don’t use the word, it usually means we couldn’t (templatewise). We aim to make things as easily understandable as possible.

Attacking Creatures Enter The Battlefield Kamigawa: Neon Dynasty Keywords Mechanics Ninjitsu Rules Shadow Thousand-Faced Shadow Tokens Triggered Abilities Your Hand