They uploaded PGP key to open directory and then verified email, what is this as not an active decision?
The presence of a key on a key server is in no way or form an explicit opt-in to encrypted email. That's what the CNAME is for.
This is seriously like telling somebody that you can be contacted on a particular phone number and then getting upset that you're getting phone calls. "Who uses the phone these days," you complain, despite having set into motion the sequence of events that led to you getting a phone call! Worse, in this analogy, it's not like you even said "only text this number"; you explicitly applied metadata saying that you would be open to a phone call.
Telling you to use a particular phone number - say through a business card, a contact page or a profile - is the analogy matching configuration of your domain to publish your intent, similar to how your domain also specify where you mail server is.
Except, it is. You can’t control of everyone out only some will send you encrypted email.
But if an email provider purportedly bringing email encryption to the non-GPG-trained masses does, it's a different story.