Yes it is normal. I had it even yesterday when I returned from a week long holiday and there were six pages of new posts.
I cherry picked the interesting ones and left the rest, yet this morning the page was empty.
There is one thing I really fail to understand, which is:
How can it possibly be normal ?... I didn't log off, therefore I didn't log back in since I was already logged in... I was inactive for maybe a couple of hours (if that), lastly, I've been a member of this forum for roughly 5 years and this "normal" thing has _never_ happened to me in the past.
Additionally, what does "Show unread" really mean if it does not show a plethora of unread posts which are visible on the right hand side. What is _normal" is for the list that appears on the right hand side to be shown in the list of "unread" with additional details since there is more horizontal space available.
The conclusion is: the behavior is illogical and, at leat as far as I'm concerned, it is _brand_ new. Never happened before.
ETA:Attached is a snapshot of what I consider "normal". The list of unread matches the list of topics with new posts in the right hand side (unlike the attachment found in the first post.)
ETA 2:@lainz,
Thank you for the link and, for the record, I did _not_ use the link you provided to obtain the snapshot I posted. I got that screen simply by clicking on "Show unread" and, at least this time, it behaved as always, that is, what has always been normal for me.