No, sorry. To put it in your terms Lemmy would be a “platform” like how you describe Mastodon/Pixelfed.

The reason I suggested mentioning feddit.org instead is because it’s what you’re using and where someone else could sign up and join easily.

Mentioning Lemmy (or Mastodon/Pixelfed) doesn’t tell people any site to sign up on, just what tech they’re built with.