I don't want to start a debate. I do suggest, however, based on my own experience this past summer that one should never depend exclusively on a POI low clearance routing.
Not every low clearance point makes it to the databases. They work fine on the well-traveled interstates but you don't need them there since the Federal regs mandate adequate clearances. The further you get off the beaten track, the more important the data is AND the greater the chance that a low clearance didn't get entered into a database.
In a perfect world you should be able to depend on such aids, I don't think we are quite there yet.