HR / Recruiter setting up interviews? The person doing the inviting might be different from previous calls/emails.
Customer meetings I get invited to often come from someone I’ve never dealt with before, but include others who I work with who were responsible for bringing me into it.
I think there's a pretty big gap between "people at my company are allowed to add things to my calendar" and "random stranger anywhere in the world can add things to my calendar".
"others who I work with who were responsible for bringing me into it" sounded to me like people at your company, who I assumed would be able to add you to the meetings. I guess I might have been mistaken
Depends on who is running the meeting. If the customer is hosting, the others I work with will provide my email to the customer so they can add me to the invite.