It looks like
ACCUMULO-259 (specifically b5c31dff) broke this way back in the day.
Previously, the static "create" method was used instead of the actual constructor to EmbeddedWebServer (changes). What it looks like is that in <1.5, the Monitor was always bound to all ports and >=1.5.0 actually "broke" this. Given that the changes were applied under a ticket that has nothing to do with such a change, this makes me wonder if this was even desirable? John Vines, do you remember at all?
I can see benefit in having the ability to not bind to all interfaces, but I wonder if we should be changing back to bind to all by default and provide the means to bind to a specific interface for that "new" case.