We do not disagree on any facts.
Yes it is a fact that referenda are deemed advisory in the legislation, but this one was offered as binding in that Parliament would have no veto. The legitimacy of that is now being tested.

I can not remember the SNP position, but the 3 main parties plus UKIP all offered a binding, in/out referendum in their manifestos.
Parliament did not challenge their exclusion from the decision in the year leading up to the referendum, and even the current challenge is not from Parliamentarians.

No-one was given any reason to suspect that the vote would not be binding and without Parliament being involved.
They were given an undertaking that it would be binding, by the government, in an official document delivered to every home in the UK at public expense.