Texas Penal Code § 32.21(1)(A)(ii): "'Forge' means ... to alter, make, complete, execute, or authenticate any writing so that it purports ... to have been executed at a time or place or in a numbered sequence other than was in fact the case."
Beard altered a signature and then authenticated it as having been executed at a time and in a place other than what was in fact the case.
Was this a forgery? Yes, definitely it was under the definition provided by the penal code for forgery. I will grant you though, that Beard's intent to defraud is borderline, so it probably wasn't a crime, or at least not a crime I think any DA would have any interest in prosecuting.