Except that we don't know for sure that "Judas" was ever sung.

If it had no tune, it wasn't a ballad; it was just a poem.

Anyway, if Taylor is correct, "Judas" isn't the oldest anyway. Taylor showed that an actual song somewhat resembling "Sir Aldingar" existed in the twelfth century. Of course, we don't have the lyrics or the tune, and there is no evidence of continuity across several centuries. The resemblance could still be coincidental.

As for "Sir Orfeo," the continuity and evolution of motifs is one thing, but if we're talking about the actual *ballad* of "Sir Orfeo," it's the ballad we're talking about rather than its antecedents.

If, for example, I want to know the name of the oldest member of the current U.S. Senate, I want the person's actual name. Just being told that old geezers have served in the Senate since 1789 won't do.

IIRC, the oldest text in Child (that is, the oldest in manuscript) is "Riddles Wisely Expounded" (Child 1). It dates from the middle of the fifteenth century.

Frankly, it doesn't have much of a story; so it isn't much of a ballad.