They say it is because the insurers regard everyone on site as a contingent liability and in the event of a claim this will be evidence that they were members or regular visitors.
The logic falls over in the next sentence where they say that the names of people joining the club after the renewal date do not have to be forwarded at that time, only when the insurance is next renewed.
So arguably you could have say ten percent turnover of club members per month, and before the year is up, nobody on the list you supplied is still a member, they are all new and unlisted.
We queried the need to supply the names of minors; the club is expected to follow the NSRA child protection policy and given the choice I would not supply the names of our junior members to anyone. However we had to comply and we did so with the prior permission of the parents and/or guardians. So yes it is a palaver.