Even then Intellectus is not Intellectus.
I would suppose if all Angels and Fallen have Intellectus, their Intellectus would have something to do with their (former) job.
In other words a very limited Intellectus for the 'small' (without an Arch-) ones.
It would not help Lasciel much, to know everything about spiders.
Urield kinda proves otherwise. In the short story The Warrior, he goes over Harry's actions & the results. Uriel also explains how Heaven specifically brought Harry into this, possibly because of these desired results.
And in Ghost Story, Uriel similarly touches on this, in how he brought in Harry, to help Molly & get rid of Corpsetaker.
Plus, people seem to be hung up on the fact that Bob can be wrong. The potential to be wrong isn't the same as constantly being a sourse of corrupted information. I think in his discussion on the Skinwalker, Harry outlines how Bob is at least generally right.
Also, those people who are doubting Bob's info on the matter, should take a second & ask themselves if they doubt him because they don't like the answer, or because they've got reason (supported by the text) to think something is fishy. I've run into this myself, but just because you want something to be true, doesn't mean it is.
Otherwise, you're trying to knock a square peg into a solid steel wall. Which just doesn't work.