The most likely reason for the discrepancy is literary license and a desire to fit within a certain poetic meter.

This definition may not turn up in any current dictionaries, but literary license isn't a sin yet.

A large amount of literary license was taken with the episodes, with several differences between recorded history and the film version.

Was there any difference between the liberties taken by journalists then and the literary license in the play?

"You've got to allow me a little literary license."

Even the decision to have the forever-muted Sunny narrate her story works as literary license.

Some literary license may have to be invoked.

Mr. Warchus won't go into specifics, but he says literary license was taken.

I have taken some literary and technological license to keep the narrative flowing.

I'd be taking extreme literary license to say I am transported back to the 30's.