Other than runway length concerns, is there a reason why this technique
would not be preferable to abruptly rotating at the published rotation
speed?

Particularly with low wing airplanes, this can produce a wheelbarrowing
effect where your mains get light, and even lift off, but you are holding
the nosewheel on the ground. Not good for the nose gear and any crosswind
gust could produce some rather interesting and dangerous effects.

Jim