My own in-head explanation has always been that the Howard women had a long and unusual history of matrilinear naming (the Howard-woman-by-marriage thing doesn't work because Beverly talks about genetic make-up both in terms of eye colour, and of why Ronin picked them). I figured either Paul Howard took his wife's name, or they met at a conference somewhere that was seated alphabetically and the name thing was a coincidence.
I would have to watch "Sub Rosa" again to hear the exact line, but maybe Felisa Howard was Beverly's paternal grandmother. She still would have contributed to Beverly's genetic makeup, Crusher's parents would have the same last name, and Felisa and all of the Howard women before her could have been the ones who kept their maiden names.
That would make a certain amount of sense, but when she's talking to Troi about the photograph of herself and her grandmother she says "All the Howard women have had green eyes, except for my mother and me."
Now, perhaps you could argue that Beverly's use of the term "Howard women" includes her mother as a woman who married into the Howard clan, but that's just a whole 'nother level of confusing.
That has a certain logic to it, but it's kinda bizarre, isn't it?
Thanks for the info, though. 
