Not a rule as such. The rule says "not + to + infinitive", but rules do not concern themselves with meaning. Following that rule with the specific expression used on the website may lead to the misunderstanding I quoted, which is why the colloquial, non-standard word order was used, but stylistically preferable is the "how to avoid" solution. It just isn't cool enough.

Google gives me lots of examples where people used "to + not + infinitive" and the majority sound quite awkward to me, so it's an expression best avoided.