Two points I should clarify.
First, I'm assuming there that everyone is basically in agreement on what would be a better bill. In fact, that may not be the case; some Democrats may simply think that a more "conservative" bill would work better (why the scare quotes? I'm not convinced there's any real ideology at work here; we call a bill liberal because the liberals are for it, not because of its inherently liberal qualities). In the event, I don't think that's what's going on here. I do think there are plenty of disagreements about details, but I strongly suspect the main dynamic here for Democrats is about avoiding controversial votes while still getting a bill.
Second, one might ask: shouldn't the press figure out for themselves whether a bill is reasonable or not? Doesn't this kind of bipartisan-worshiping Broderism make them vulnerable to one side simply taking an extreme position, leaving the press to move the middle far to that side?
To the latter -- yes, but good reporters can see through that sort of thing and good politicians to help them see that; indeed, I think that's a lot of what's going on now. To the former: no, the press really can't just objectively figure out what's reasonable and what's not. There are no available standards.
Basically, bipartisan voting used to be a good-enough proxy for reasonableness, and now it isn't, and the good reporters out there are trying to figure out new indicators. That's hard work, but doing that hard work is the standard to hold reporters to, not whether they try to figure out whether the underlying bill or policy position is reasonable.