This is not definitive about this particular group, but elsewhere one can easily find evidence the Bwiti don't think these ceremonies are for everyone.
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http://www.awakeninginthedream.com/moughenda.htmlInterview with Patrick Moughenda, Bwiti healer
"What might be secret is the Bwiti stuff, the rites...First of all, Bwiti at first was pure and African. From day one it was African, and there's a group of people in Gabon who will not share anything, who kept Bwiti a secret. They wanted a secret religion. Most Gabonese from different tribes are going to have a heart attack to find out you're initiated Bwiti."
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Moughenda himself is denounced many other places online and deserves his own thread. But even he admits the great majority of believers don't want just anyone initiated.
A big part of the faith is healers who take iboga. Just like with ayahuasca and peyote, too many outsiders imagine it's a quick fix for anyone curious or desperate.