I'd look at it 2 ways. If a diagnosis is given (and they're not given easily!) then I think you just live with the diagnosis until your child a) develops more symptoms in which case you'll be glad that you have it as a passport for 'some' support; or b) your child doesn't get the diagnosis and you go back to school armed with the knowledge that they were wrong. the child then doesn't have to declare their diagnosis. its their choice when they get older at least that's what i was told.
Wow, unusual to hear of this really, Most of us have had to battle and chip away for years to get a diagnosis, let alone recognition of issues from school.
I've had SENCO 'tell me off' in the playground as I've gone to too many people (teachers) for help (no one listened or communicated between one another). This is because they didnt see issues. DS was diagnosed in year 1.
I know I'm babbling but what Im trying to say is that they saw nothing in year 1. DS now has dx of ASD, SPD, dyslexia, visual stress, and now has symptoms of OCD that have affected him massively. He's always struggled educationally but never far enough back to be of concern.
Ive been requesting them to acknowledge his needs since reception. Now. school are now applying for support due to the deterioration of his condition, education, happiness and everything else.
I sincerely hope your DC never deteriorates and needs any of this support, but from my own experience I would recommend you did the referral while its on offer, just in case. Maybe even for peace of mind if no dx is forthcoming. Good luck.