I did find that it worked consistently, but it displayed only one post per thread, so what you were seeing was the last message in each thread that had a new post. So that's why you saw Minja's replies to Bobubas but not his messages in the listing
YaBB support has clarified how the feature works and the way they'd worded it was definitely misleading. It doesn't actually bring up the 10 most recent posts - it lists the last post that's been made in the 10 most recently updated topics and sorts those 10 posts by date/time in descending order.
In other words, say I come to the forum and read 7 different topics and I decide to make 1 post in 6 of those topics and 4 posts in the 7th. If I then use this feature, what will come up are the 6 single posts that I made in the 6 topics along with the
last post I made in the 7th. The other 3 posts that I'd also made in that 7th topic won't show up because they aren't the
last post in that topic. In their place 3 other posts that were made to 3 other topics before I came to the board will come up to make up the total of 10. (It
is somewhat confusing, so I hope I've explained that all clearly.
)
Anyway, I've changed the wording in the link so that hopefully there won't be any more misunderstandings.
And maybe someone should think about sending the YaBB developers back for a refresher English class because it seems that they were all absent the first time around on the days their teachers explained what the words recent, previous and next mean and how to use them.