UW is on the decline I believe. It's about intent. They didn't expand the Qbank to 3800+ because that's helpful to students. They did it for themselves as an effort to try to drive out competition from, e.g., Amboss, Rx, etc.
People average at least two Qbanks during their prep nowadays. UW has always been the gold standard. Then students will pick a second Qbank. So UW thought, "Well if we just make our Qbank essentially two Qbanks in length, then people will just do ours." But the result is now it's too long/superfluous. They seem to be engaged in some deleterious runaway effect.
The focus needs to be on the NBMEs because those are the real exam, yes. For Step 1, the aim needs to be to memorize forms 20-30 (even though the online ones are 25-30). And that just scratches the surface truthfully. I've observed repeats from forms 6-18 on 20-30. The Qs are repeated everywhere. And certainly on the real exam.
For 2CK, the aim should be to memorize forms 4-8 + the Clinical Mastery Series subject-specific forms.
I see it with my students that memorizing the NBME Qs leads to best results. Think about the number of people worldwide who do UW 2-3x and still get mediocre scores, yet UW is still the gold standard. It's just branding and people blindly following.