Aha! Fund the wall and the government is open, again. Sounds like extortion.
I think it's just a demand to shift the blame for not re-opening the government to the Democrats. Otherwise they would be the ones demanding spending and blaming the GOP for obstructing the spending bill.
I'm actually surprised the Democrats don't want the wall. They like fiscal stimulus projects and they like keeping nations separate, so why do they dislike the wall thing?
Imo, it's only because it creates a monument to national borders that will instigate protest for decades once built. It will be like the Berlin Wall, hated, and eventually demolished. Democrats don't want nationalism to be that overt and thus subject to resistance.