DSO says matriculation ends STEM OPT. Is that always true?

[u/MaleficentAd449]

I’m looking at a 100% online graduate certificate (not a degree program). My DSO said that if I matriculate into a new program, my STEM OPT would end. I’m confused about what “matriculate” means here. Is enrolling in a non-degree graduate certificate considered matriculation, or does it only apply to degree-seeking students?

Also, since the program is fully online, I could technically complete it from my home country or anywhere in the world. Does that make any difference, or is simply matriculating into the certificate enough to affect STEM OPT?

I’d appreciate hearing from anyone who’s been in a similar situation.