I do not know how volunteer organisations work in France but in the UK there are no formal interviews, background checks,or references required for voluntary work at all, unless you are going to be working with children or very vulnerable people. I have had a few voluntary posts since I retired. For my latest post as a tour guide I had health and safety training, and safeguarding after I'd been working there for a while. Most big organisations in the UK like English Heritage, the National Trust, the major Cathedrals,(the guides), WRVS (hospital tea bars),charity shops, RSPCA, most big charities rely on volunteers.
I did a similar scheme to Workaway in the UK. No interview or checks. It's not unusual.
I feel that if volunteers had to go through the same checks that paid workers did, there would not be many people volunteering and the organisations would not be able to run. Some organisations run on a shoestring budget relying on public donation. They would collapse if they had to use more paid workers. As a volunteer you have to work hard for no pay. You would have to really want to do it, have an interest in the organisation, be dedicated. People who are not suitable soon leave. This is just my personal opinion.