Yes, it does seem odd, especially in light of the fact that Reuters seems so anti-Bush. It doesn't seem logical that they would omit the "al Qaeda" preference for Bush when first publishing the letter. They could, and probably would have made the most of this.
Perhaps this was an add on by some al Qaeda/Kerry friendly sources?
I think it's especially interesting that this development shows up late in the day - and all of the original postings of this report on the Reuters website were pulled just a few minutes ago. The pages were left blank for several minutes, and they have just been refreshed with the new "Bush" version...