Why would this regulatory board go after an entrepreneur when he’s clearly not in the business of official land surveying?

Regulatory capture. Surveyors don't want people going around them. Protectionism.

It'll likely get dismissed, hopefully, like Oregon's lawsuit against Mats Jarlsrom for "unlicensed practice of engineering".

https://www.thedrive.com/article/16790/oregon-violated-rights-of-man-who-challenged-timing-of-traffic-lights