Maybe he states them as both being signed 'Santa Claus' just because it's simpler to do so. After all, in Harry's mind the author of each note is very likely the same person, so the two notes may as well have both been signed 'Santa Claus'. It potentially saves the time of having to explain (what is to him) a foregone conclusion. Whether or not that's a detail Harry would normally skip is up to you I guess.
Of course it could just be an authorial mistake. But I'm willing to give Eliezer the benefit of the doubt on a minor point like this.
Maybe he states them as both being signed 'Santa Claus' just because it's simpler to do so. After all, in Harry's mind the author of each note is very likely the same person, so the two notes may as well have both been signed 'Santa Claus'. It potentially saves the time of having to explain (what is to him) a foregone conclusion. Whether or not that's a detail Harry would normally skip is up to you I guess.
Of course it could just be an authorial mistake. But I'm willing to give Eliezer the benefit of the doubt on a minor point like this.