Oh, look! It's exactly what it says in the withdrawal agreement

Brexit
  • UK lawmakers must set out terms of how to avoid no-deal Brexit
  • There are no technological solutions proposed that would solve Irish border issue
  • We have no choice but to ramp up no-deal Brexit planning

If you're still wondering why UK lawmakers cannot get behind May's deal, that's basically it. The latest change/assurance allows for the UK to "unilaterally" apply for arbitration to exit the backstop should it be able to justify that the EU is "intending to trap the UK indefinitely".

Funny that "unilateral" means going through an arbitration panel that will be subject to EU laws. And all the EU has to do is reiterate what Donohoe said in the headline comment and that basically counters all the arguments set out by the UK. Good stuff.