I've seen this mentioned before this would be suppliment to the exact code requirements in the all the of Article 250, Right ?
Is it just more of a Local AHJ thing? Regional practices?
As Mr. Kennedy stated above the metal water piping SYSTEM requires bonding.
Water heaters, softeners, filters, contain di-electric breaks, just the sams as a repair of a metallic piping system with pvc pipe causes a break in the piping system continuity. Thus the requirement for a hot to cold "bonding jumper". Hot to cold is a misnomer, all breaks require a "bonding jumper".