It seems as though questions that are being marked 'primarily opinion-based' are, in fact, off-topic for one reason or another. For example, each of these are off-topic because they're asking for off-site resources.
According to this meta post one of the reasons for the changes was to:
be able to query and analyze the reasons provided via the "other" off-topic option in a fairly simple fashion
It seems that to meet that goal of being able to provide useful statistical analysis, avoidance of mis-marking these is useful. Yet, it seems like the mis-marking does occur a great deal. I'd assert that this is because the 'off topic' reasons are behind a second mouse click 1, while a catch-all option ('opinion-based') is available immediately. Further, in thinking about this, the whole 'off topic' labeling is subtly inaccurate: a fast-and-loose interpretation of asking for a library isn't 'off-topic'; it is opinion-based. (Because, really, they are asking for an opinion, and thus there is a semantic overlap between these two categories).
Is it possible to surface the 'off-topic' reasons more prominently? I recognize the UX issue here, of course. Failing that, is there a way to discourage voting everything as opinion-based in favor of more precise categorization?
1 I'd prefer not to get into an extended discussion about the fact that people should click through and are therefore doing it wrong.