From the Indian technology that spawned remarkable stone beadmaking, the sequence would be to finish the exterior before drilling. A drilled bead can be considered to be finished.

It's possible that the workers did not want to waste time with drilling, for a bead that would not survive the previous treatments, that included firing. And perhaps they thought that a bead-blank that survived the previous treatments was sound enough that it would probably not break during drilling. I'm just speculating here. But it is well known (via Kenoyer) that this was a typical sequence. Plus, the occurrence of otherwise complete finished beads, that remain imperforate, suggests drilling came last, or practically last. (It would not surprise me if the final high polish might be done as the final-final treatment.)

I have documented a few beads that are imperforate, and that only have perforations that intrude a CM or so into the bead. I suppose these beads were probably capped (as with gold) to provide their hangers.

Also, we have the instances of Central India and Burma—where apparent factory sites yield imperforate beads, that when recovered (in recent times) have been drilled to be exploited as wearable beads. Apparently, a great many of the "Sulemani" beads circulating now are from factory sites—and some are recently drilled. Nevertheless, the beads are not revealed to be all this. They are routinely represented as "ancient"—as though they have been worn and cherished for centuries. (Which would not be the case. And, the increasingly high prices might be compromised if people knew the truth—that these beads probably cost almost nothing, compared to the amounts demanded.)

JDA.