Just by way of explanation:
As one of the authors of the manual, I periodically do a search of all bugs on Flyspray with category "manual" to see what corrections need to be made. Also, I always review the Flyspray entries when I sit down to work on the manual. On the other hand, if a correction to the manual is posted on the forums, I may see it if I happen to read that thread, but there is no guarantee. Even if I do see it, however, it's unlikely that I will address it immediately as I am pretty busy right now with other things. By the time I next sit down to work on the manual, I may not remember reading that thread.
The bottom line is, if a correction to the manual is properly posted on Flyspray, I will see it, whereas if it is posted on the forums I might see it.