SN session aren't just about it being quieter.
I take my child with ASD to SN sessions at soft play, the cinema and other facilities. He can't cope with big crowds and noises, for sure, but it also means I can relax knowing he's not going to be bullied or teased for how he behaves or what he says. He's incredibly vulnerable and often comes a cropper in standard sessions.
Not only that, but I don't have to put up with people looking or commenting on his behaviour.
If this was a SN session, then it should be for SN children. The idea from a PP that since it's hot, NT kids should get preference can suck my chewable wristbands.