Fairly certain he just meant the use as a descriptor makes sense if you just take binding as an adjective (restricting) describing the type of gear as opposed to a verb/noun describing its spiritbond state.

binding adhesive
binding promise
binding handcuffs
etc.

ie -
binding as opposed to nonbinding/unrestricted
vs.
binding as opposed to bound in the sense of present and past participles describing its current stage of spiritbond.