> I thought that was Tomcat or was Tomcat just the servlet reference implementation

Tomcat itself has never been an official reference implementation of anything.

Tomcat implements various Jakarta EE APIs, most centrallly Servlet indeed, but also JSP (Jakarta Pages) and JSTL (Jakarta Tags), WebSockets and Jakarta Authentication.

The initial Tomcat was donated to Apache, then used back in GlassFish. GlassFish WAS the reference implementation of Servlet (among others), so indirectly Tomcat kinda was the reference implementation indeed. But just a fork of its code via GlassFish.