The problem for the DUP is that much of their core support comes from evangelical Protestants who adhere to strict principles, and as you would expect have strong moral objections to abortion, which will be decriminalised later in October, automatically. The are annoyed with the DUP for allowing this to happen when they could have done a deal on the Irish language, got the Assembly back up running and prevented abortion change.I wonder if this is intentional. Arlene is known to be very hard anti-nat, but is not reckoned to be so rightwing on social issues. Was it at conference that she had the DUP's first lesbian councillor sitting immediately to her right? (edit - 3 to her right)
I'd view abortion by default as a favour done by Johnson to the DUP. It takes it out of the equation without the DUP having to vote on it. The party no longer has to spend time debating the issue, and will not tear itself apart as a result. They can pass a motion deploring this action by Westminister and move on.
Now they can focus entirely on the real issue: how to keep the taigs down.