[gelstudios]

I think certification gives the holder some potential credibility in a narrowly defined area IF an employer chooses to believe that a specific certification sufficiently covers the skills required for a business process.

That is clearer for roles that primarily need to operate software packages (word processing, CAD, etc) or systems where there is training content created by a solution vendor (cisco, juniper, etc), than it is for a multi-disciplinary "squishy" role like product management.

Consider that a product manager role might greatly by company size or by level of product / market fit. I'd say that an employer shopping for a PM might be looking for a combination of: subject matter expertise, deep knowledge of a specific market, and maybe a track record with KPIs. All of which are probably not easily evaluated by a common certification.