the biggest example of this imo is the chinakhov pick from a few years ago. he wasn't on the public boards at all, but he was in the top 10 on the jackets board.
they picked him at #20 and got a load of shit for not trading back. but all they saw was a top-10 player on the board available at #20. the outsider perspective was an enormous reach, but based on their board he was an enormous value pick.
had they made assumptions based on public boards, and traded down, they may have missed out on chinakhov. is the marginal increase in draft capital via trade-down worth sacrificing a top-10 player who you can get at #20? nope.
that said, team boards start to show more variance after the top 10-15 picks. with the jackets picking fourth this year, they may have similar grades on the 4th-10th guys on their board. if a team makes it worth their while to trade back, they may still be able to get a top-5 guy on their board at 7 (ottawa) or 9 (calgary) while netting an additional first-rounder.
if they get on the clock at 4 and one of their top 3 guys is still there, though? then you make the pick and don't think twice about it.