A similar problem might have applied to Vulcan/JP233. The low height in a AAA zone would have been very dangerous. The delivery speed may also have been an issue.
With dumb bombs the time interval could be adjusted to ensure the proper interval between bombs. Did JP233 have a variable time dispense control?
The Vulcan doctrine was for a nuclear laydown attack as low and as fast as possible. With 117TUs a conventional laydown attack was feasible but not against a heavily defended target with AAA. There was a preferred option against AAA of 8,000 feet minimum.
Against medium SAM 18,000 feet was deemed acceptable, but all these were predicated against Soviet weapons in the early 70s.