I'm not a musical expert, but I tend to agree that Tim is using his naturally high voice to sing the chorus of Ella Jean rather than an artificial falsetto. Falsettos usually are a far cry from the natural sound of a singer's voice (reference Fast Company). That's why I hate it when Glenn pulls out the falsetto. It turns his rich, textured voice into a bad Bee Gees impression.

Actually, I find that the catchiest part of the song and I often find myself humming it. "Ellllllla, Ella Jean...." Seems I'm in the minority!