CFPs get this stuff wrong all the time, as is the case with that CFP's answer. They generally cannot be considered to be authoritative. Trust the statement in the IRS Pub.
Also see CFR § 1.219-2(b)(1) which includes, "An individual whose compensation for the plan year ending with or within his taxable year is less than the amount necessary under the plan to accrue a benefit is not an active participant in such plan." In other words, if the individual is not receiving any compensation from the company and is therefore not continuing to accrue benefits, the individual is not an active participant. An individual who is no longer employed with the company and is already receiving the pension is not continuing to accrue additional benefits under the plan.
<a rel="nofollow" target="_blank" href="
https://www.law.cornell.edu/cfr/text/26/1.219-2">https://www.law.cornell.edu/cfr/text/26/1.219-2</a>
