That would have been one way to implement it, certainly.

The actual implementation was something like this:

  const char *cluster = "ex";
  uint16_t enc_cluster = (((uint16_t)cluster[0]) << 8) & (uint16_t)cluster[1];

A proposal to reserve the high bit to signal a "long name" was unfortunately(?) not accepted.

This was nearly a decade ago, so things may be different now. You'd have to ask someone who currently works there to tell you what their cluster names look like.