don't know the exact origin of why the unusual foot shape - could be for pips or the spoon (there are specially shaped/designed spoons for grapefruit) - but for reasons of association, I've always called bowls with this flared foot shape, 'grapefruits'.
I get the impression that tinned/canned segments of the fruit are more a post WW II invention, rather than using a spoon to eat the fruit from its skin, for which you need a bowl - I recall my mother cutting and putting mountains of sugar on the fruit halves on a Saturday evening, in bowls They were always the white variety which were very sharp to taste - don't recall any pink ones then, and this really sweetened them for breakfast on Sunday morning - Sunday breakfast seemed always to be considered more posh than other days of the week.
I notice that Mrs. B doesn't index the word grapefruit in the early C20 revised edition of her book, although it does occur in later mid C20 editions, and try as I might I can't find info on the history of the design of the flared foot shape. I think this unusual foot design is also shared by sorbet and sundae dishes, so bit of a generic thing maybe.
I still don't consider this one to be for grapefruit - although you can eat anything out of anything if you really wish

I didn't intend to collect these bowls Anne, they seemed to arrive without any special effort, and apologies in advance to bat, but I forgot to include what is possibly my best one ........... it's a Walsh 'Pompeian' example in blue (with backstamp), and with a ring to die for ..... dates to somewhere in the 1940's possibly.
Again, my apologies to the op for digressing and being long winded