I never found anything substantial, other than a complaint from one of their promoters.
It seems they operate on some sort of referral program where people get paid by signing up new members.
They can also be found spamming the comment sections of other nudist websites and blogs.
I’ve heard a few strange stories here and there from people who’ve tried them, and none were positive.
Most likely, the members you’re seeing on their sites are not real.
As Nudie Lee pointed out in response to a nudist dating question, the internet can help anyone looking for that special person(s), including nudists.
There are online dating sites galore, and many couples meet each other this way. There are a few social networks for nudists, but there are no networks just for nudist dating.
Any such website you’ve seen is most likely not what it claims to be.
There is one company that’s been periodically creating the same nudist dating site over and over.
They just keep using new domains, such as nudisttodate.com, nudistpassion.com, nudistpersonals.org, etc.
All of these sites follow the same basic format with a sign-up form and preview photos of supposed “members” available to date.