The 3.5 Scent rules as written have a lot of rough edges. Enough so that I would not expect a DM to adhere to strict RAW.
In terms of this story, Belkar has established that he is both a ranger and a skilled cook with an acute sense of smell/taste who spends personal time worrying over spices. We see him spreading herbs. That he could mask a scent makes a lot more sense than you average ranger, and as a DM or reader I would find this idea attractive enough to agree to.