The EU is not as adamant as it seems. German main channel TV news just said that if the deal gets rejected in third attempt, they would hold another Brexit summit next week and then decide that
they will offer the UK a longterm delay, I assume of several years, so that no no-deal- Brexit happens. And it also means the Ul stays as member of the EU until... well, until the end of time, it seems.
When Western diplomats talk of ultimatums, I just must break out in laughter.
Lets face it, either the UK
1. gets negotiated into eternity and all the time stays as member of the EU, or
2. it accepts the surrender deal and stays in the customs union and having no rights to negotiate its own independent trade agreements with other non-EU nations and thus it would be a vasall of the EU once the Backstop has been activated, needing to obey but having no say, or
3. it withdraws the Brexit and stays in the EU.
You are ours, from then until eternity!