Northern Ireland Budget Bill

Is it not the case that Sinn Féin has opted out since the Brexit decision? It has played on that decision, making a calculation that it will stay out of the Northern Ireland Assembly while playing up fears of a hard border and a hard Brexit to provoke talk about a border poll, which plays well to their constituency. However, as the Secretary of State has often said, there is not going to be a border poll because there is no evidence that people want to change the status of Northern Ireland.