You joined a special interest technical group which is specifically for professional networking and informal meetups and you sent a general email to the entire group which led to a hiring process. Nothing about that is “cold calling” or “cold email”.

Likewise, the posted article describes a Tweet from someone who announced they were hiring specific skilled professionals for an open position, and the author privately responded to that informal job posting. That is not a “cold call” or “cold email” just because you didn’t go through Indeed dot com.

But if you do send actual cold emails, then you undoubtedly have the prerogative to post and say that “<Company> Ghosted Me During the Hiring Process!!1” /s

Sending an unsolicited email to a person or a group is a cold email. There's nothing to bikeshed here.