I don't know if this qualifies as a bug. The idea is the messages group up if they are consecutive in the stream of protocol messages that coming in. Even though the UHTML messages are hidden when the next one arrives, theres still a uhtml message there separating them.
The better questions are:
- is this desirable (probably not) or undesirable (doesn't personally bother me) and
- is this worth dev time to fix/implement (right now? probably not unless someone else wants to take a crack at it)