I don't see it as a massive win for the DUP. Certainly the dice would appear to have fallen kindly for them. But the overall Unionist vote continues to decline.
As far as a proxy UI vote, it is the DUP that is running scared of a border poll. For sure, such a poll if held today would carry the status quo. The issue the DUP have with a border poll is that if one were held, they would have no option then to recognise such polls a the means to determining the future of NI. If they accept the result of such a poll today (because it would be in their favour) then would then have to accept the result of such a poll in the future if it ever went against them. That is their fear. They believe the sovereignty of NI lies with the British monarch, not with the people. That is why they are against a border poll.
And while the DUP may never agree to a border poll, there is a strong case now I believe to bring the matter to the courts for a decision. The British government is legally bound to facilitate such a poll if there are reasonable grounds to suggest there is a need for one. SF hold 7 Westminister seats, in assembly elections, they are 1 seat behind and 1,000 votes behind.
The conditions for a border poll are emerging fast, in my opinion.