I'll give you that they didn't fully impose themselves against United or Soton, but those are two good teams they were playing away. West Brom they absolutely dominated (XG 2.59 to 0.21) but couldn't find the net, which happens. They had better XG and XG differential in that match than in the 5-0 yesterday.
Unfortunately, I think they're just really, really good. They stumbled a bit out of the gate as they were dealing with the abbreviated pre-season and still integrating Dias and finding their feet, but since around mid-late November they've been not far off the very high levels of a few years ago.
This is a crazy season and there could still be some twists and turns to come, especially if they have some injuries, but they are clearly ahead of everybody else in terms of form over the last two months (if not in the table).