That is a key distinction. My statement was misleading. They do not deny their membership or their existence, hence, not a secret society. I stand corrected. Well said.
The membership was not a secret, but I think they were a secret society in that much of their material was. Initially, Masonic books were to be returned to the society upon death of the member. Of course that would never work in the long run. These days, their beliefs (and maybe their rituals) seem to be freely available from various sources.