This only in effect, restates what has been the EU position since day 1. The EU demands a WA is signed and ratified by the UK Parliament before it even begins to discuss Trade issues. The UK's approach as always been the opposite, to agree (optimistically, over a two year transition period) a trade deal, then a WA agreement can then be reached. Each side (understandably) reluctant to give a hostage to fortune, to the other side
So in three years (plus), nothing basically has changed at all. Despite May changing her mind and agreeing to the WA being agreed first she did however always imply "nothings agreed until everything is agreed" but then seemed to have change her mind on that; its no wonder the EU read the wrong signals from us. Now with Boris seeming to want to focus on getting some sort of movement on the back-stop, he is giving the impression that this will be enough to get both sides (who lets be honest are both dreading a no deal outcome) to agree to some sort of 'eleventh -hour' negotiated deal.
The problem is, that as many people have been saying, a lot more is known now about what Brexit means, or what it doesn't mean, than at the referendum. However a little learning can be a dangerous thing, most leavers now know things they didn't know, principally that the only way they will be likely to get what they want in Brexit is through a no deal and remainers know any sort of 'deal' agreed is less than what we have now and so revoking A50 is the only way out for them, that's why Swinson is betting the house on this for an upcoming GE.
Corbyn's been playing for a GE all along and it has to be said he has played a 'blinder' on that one, but he's missed the boat, by the time the GE, (known as the Brexit GE) comes along Swinson will have stripped him of the mantle for Revoking A50 and the Tories/TBP will have stolen a number of his northern seats. Jeremy's like a player running the full length of the pitch evading tackle after tackle, rounding the goalkeeper, then firing wide!