Hi Felix,
I am using this naming pattern deliberately, precisely not to achieve what you want.
In other words, it's a good thing, that all tiddlers tagged Journal are not listed under Journals.
Why?
Because that way I can have other tiddlers relate to the concept Journals via tagging without actual Journal entries ending up in the same list.
So, my summary for these two reads:
Journals - about daily journals and such
Journal - a list of [[journal entries|Journals]]
...whereas the tiddler Journal lists titles of all tiddlers tagged Journal but the Journals tiddler actually shows the 5 most recent ones, fully.
Creating a new tiddler and tag it Journal... not too hard of an exercise I find. Otherwise, I can always open the tiddler Journal and then use "new here" at that one if I'm being lazy. ;-)