If we are on the level of terminology, the more accurate statement would be that WIF is a 51 char string with certain chars excluded.
Yep, you're right. WIF as 306 bits doesn't really exist outside my convenient mapping from 6 bits onto base58 space. So my 306 bit definition fails

I take it back.
I mean. Isn't that expected? When encoding values using Bacon you use 5 bits but you only have a dictionary of the characters you need.