The only illustration whch seems to support the use of a 'cocktail-stick' type spear from antiquity.
The 'Franks' casket is a whalebone box made in Northumbria c.800AD.
This is unfortunately not a viable piece of evidence. If one takes all the illustrations on this box then this single figure holds his spear in that way. All others have a spear longer than their height which look like spears shown in manuscripts.
The one figure can be explained as due to the artist's inexperience, maybe. As in the similar awkwardness with which he shows the archer's stance due to space considerations and the shields depicted proportionally smaller than reality.
In addition, some scholars believe these few figures are meant to be giants, which is why the spear is held like this.