Again, this is down to opinion. The WA did (and still does) allow the UK to leave the EU, it's just that those MPs didn't agree with aspects of it. You could say they were at the time thwarting the will of the people by voting against it - although I realise this is a stretch as they wanted a more Brexit-y Brexit than was on offer as part of the WA.
And WP, I am aware the WA is only the first step - following by the non-binding political declaration.