I don't know about Mermaids but GIRES have a toxic online training session for adults working with children where in a role play they insist on immediate affirmation and confidentiality - for both a primary and secondary child.
I’m a DSL in a primary school. I did that online training when I was told by the then PSHE lead for our local authority that schools should use the Allsorts schools toolkit and should not use the Transgendertrend toolkit because it was not compliant with the Equality Act. She suggested the testing because I clearly needed educating about trans issues.
The training was the biggest crock of shit I’d ever come across. It was impossible to progress through the questions unless you embraced total affirmation and ignored all the safeguarding training you’d ever done.