On the first bolded statement, that only applies to EU members. Switzerland and Norway don't have to accept deeper integration. UK got an exception to that as well.
On the second bolded, what we're seeing now is a rejection of staying in the trade area that the UK allegedly always wanted to be in. Because, if you hear the ERG talk, there's more opportunities for the UK outside of it and it can strike better deals for itself without the weight of the EU28 behind it. The treaty of Rome in 1957 that started was about creating a common market and customs union. Yet now the UK wants to leave even that.
If the UK wants to be in the Customs Union alone, or the Single Market fully, it can choose to do that without a deeper integration. But being in any kind of union means that you're not in full control of your trade policy. It's a group decision. And after years of filling the ears of voters with hate and suspicion of the EU as well as inflating our own self-importance, we're reaping what we sowed. Which is that people want out as point of moral principle that is not underpinned by any logic.
Why does that quote have my name on? I didn't say that.