Wait, is that what headless means now in the agency world!? I remember headless meaning the CMS wasn't the software serving the initial request, it just provided an API that some HTML/CSS/JS on S3 or something would consume.
Yes apparently so: my customer is a very intelligent research director at a well known company. He was very excited to tell me about going "headless", and I was very confused for a solid 5 minutes before figuring it out. He told me that this was the term his vendors were using.