Lots of sites would like to make the paywalls immediate, but they won't get ranked highly on search engines if they don't show the article's content to a web crawler.
So the usual approach is to load the content, then hide it as quickly as possible if an unauthorized human is viewing the page.
Edit: OK, I just answered my own question. At the top it says:
"You have 2 free member-only stories left this month. Sign up for Medium and get an extra one"
You only get ONE more story to read after signing up? That's very misleading.