looks as if expressly written for interlineation.

Besides a marginal gloss by a later, fourteenth century hand, there are two distinct sets of variants, in different writings, interlined and running over into the margin.
These variants are much more numerous in the prose than in the verse.
The first set are in the same hand as the text, the second in another hand: but both of them have the character, not of variants from some other MSS., but of alternative expressions put down tentatively.

If either hand is Saxo's it is probably the second.

He may conceivably have dictated both at different times to different scribes.

No other man would tinker the style in this fashion.