I don't think that is always the case. Often service providers will have staff toilets and service users/customer toilets. I am a member of an
Organisation that suddenly, without consultation to its members , changed its toilet provision, having now some gender neutral, and keeping the more hidden and hard to get to, one or two options as single sex. I contacted them through their member survey about this and asked explicitly for communication. They have refused to engage with me at all on this matter. My subscription is quite a lot per year, it is not a sport club and I feel their response is absolutely inadequate. In my reply on their member survey , I did state that I had concerns as a member and I hoped their staff had not been pressured into accepting similar arrangements. So the guidance is not that helpful to me. I know plenty of gay individuals attend but I have actually never seen a trans male or female, and it is an event where dressing up is welcome.