I did not see the issue raised in any posts of either link you posted
The links appeared to be concentrating on the size of the package/s as well as questioning the necessity for the package/s in Xfce.
Maybe I missed something obvious ......
So the original question remains ....... why were those packages not showing under the upgradable status, but did get marked for upgrade if I Marked All Upgrades?
What is the difference between the two schemes/methods?