I disagree with their answer for the for the following reasons section 250.53 D(2) requires the supplemental grounding electrode but also states a rod, pipe or plate must comply with 250.53A and there it states a single rod must be supplemented by an additional electrode, excluding water pipe, or meet the 25 ohm requirement.
250.53 Grounding Electrode System Installation.
A (2) Supplemental Electrode Required. A single rod, pipe,
or plate electrode shall be supplemented by an additional
electrode of a type specified in 250.52(A)(2) through
(A)(8). The supplemental electrode shall be permitted to be
bonded to one of the following:
(1) Rod, pipe, or plate electrode
(2) Grounding electrode conductor
(3) Grounded service-entrance conductor
(4) Nonflexible grounded service raceway
(5) Any grounded service enclosure
Exception: If a single rod, pipe, or plate grounding electrode
has a resistance to earth of 25 ohms or less, the
supplemental electrode shall not be required.
(D) Metal Underground Water Pipe. If used as a grounding
electrode, metal underground water pipe shall meet the
requirements of 250.53(D)(1) and (D)(2).
(2) Supplemental Electrode Required. A metal underground
water pipe shall be supplemented by an additional
electrode of a type specified in 250.52(A)(2) through
(A)(8). If the supplemental electrode is of the rod, pipe, or
plate type, it shall comply with 250.53(A).
supplemental electrode shall not be required.