I think the bolded part is incredibly important and occasionally dismissed. The prospect hitting .300 without walks who isn't striking out either is a VERY different animal than the one hitting .300 without walks who is striking out a lot.
Especially when there's power involved in driving that average, the strikeouts (or lack thereof) portend an ability to handle more advanced pitching. There's nothing wrong with getting your OBP through hits -- in fact it's preferable. But if you're doing that because you're beating up on bad pitching (while getting dominated by good pitching), you're in for some trouble when the bad pitchers stay behind in the low minors and you try to advance. How will that average hold up when you start facing guys who can command their breaking stuff? You need to either be able to hit that stuff or lay off of it and it's hard to see that ability in the low minors.