...it is hard for me to imagine that they won’t be able to get the 216 votes they need — although they obviously don’t have them as of today. Otherwise, they would have already voted.Well, sort of. There are real procedural roadblocks that take time; there are also negotiations that have nothing to do with having the votes that take time. On the first, it really does take CBO a while to score a bill, and the House really does need the bill to be scored before they vote on it. Well, "need" is strong; I suppose they can waive anything, especially in the House. But given that the Dems want to get the patch part through the Senate intact, so the House doesn't have to vote on it again, and that they apparently don't want to try overruling the Senate parliamentarian, they're (again, apparently) trying really hard to tailor it to avoid any procedural challenges. That requires them to know exactly what they're doing, which requires giving CBO time to score everything. There's also a commitment by the Democrats to have the bill available for 72 hours...again, they can break that, but not without at least some cost.
On the other possibility, it's certainly possible that two or more Members of the House (or Senators), both committed to voting for the bill, could be negotiating on one or more issues. Indeed, that's almost certainly one of the things that's slowed the bill during February.
Pelosi might have the votes now, and might not. Most likely, she knows that she will have the votes, and has for at least a couple of weeks, without knowing for sure which specific votes she has -- one or more Members may have signaled that they were with her only if she needed their votes, and her main task is just coordinating those Members, not really flipping any real no votes to yes.