Enkidu: Rival or Substitute?

A colleague at Temple asked me the other day about a curious little reference in George’s popular translation of the Gilgamesh Epic:

For the goddess of weddings was ready the bed,
for Gilgamesh, like a god, was set up a substitute.
(Tablet II, 109-110)

What does this mean? What is the concept of substitution to which the text is making reference?
George’s more scholarly work has:

a-na diš-ḫa-ra ma-a-a-al [x x] ti [x]
a-na ^dgiš-gím-maš ki-ma ili(dingir) šá-ki-i[š-š]ú pu-ḫ[u?]

For Išḫara a bed of […]…
for Gilgameš, like a god, a substitute was in place.

George, himself, has problems with a substitute (pūḫu) in the text of the Standard Babylonian version. The Old Babylonian has rival (meḫum). George wonders if the change from the latter to the former is related to rituals of the substitute king (šar pūḫi). George comments:

However, I cannot see that the narrative of Enkidu’s challenge is well served by reference to this royal substitute. The plot requires a rival, not a replacement. Perhaps the Middle Babylonian editor, failing to understand the long-obsolete custom which was, it seems, the context of the older version of the line, sought instead to connect it with something he knew, the ritual of the substitute king. In doing so he destroyed the line’s original reference and failed to replace it with anything meaningful. (The Babylonian Gilgamesh Epic, 1:459)

Yet, I wonder if it is even this simple. While the custom of the substitute king was around in the Middle Babylonian period, it was more prevalent in the Neo-Assyrian period. The only manuscript in which the sign pu is preserved is the Neo-Assyrian tablet RM289 from Nineveh. Perhaps the scribal updating was even newer than the Standard Babylonian edition.

Perhaps the reading in RM289 is itself a scribal error?