If I remember correctly some time back Mr. Texas posted that the orange Grapefruit did not have a very good taste. - Millet

Chironja, there used to be trees at a Dept Ag research station( Australia )
Fruit was certainly interesting, but nothing unique. Sort of exactly 1/2 way between both OJ and GF, without the 'zing' of either. I thought if you mixed orange and grapefruit juice you would be pretty close, so probably wouldnt bother to grow it in this climate.

Poorman, what I tried was fairly similar to Smooth Seville, ( probably a sour orange/pummelo hybrid ). Both had very similar internal structure and seed shape, except that poorman was a milder flavor and lighter color.
The bitterness of sour orange, ie the Chinotto type flavor, was certainly there.
I would guess it's not a orange grapefruit hybrid at all.
That said, it is not common at all here, and you would have to be careful of naming confusion, as Poorman and NZ grapefruit could easily be mixed up with other types, or even variable seedlings.

I could certainly believe that 'Triumph', 'Royal', 'Imperial', and 'Isle of Pines' are actually the same clone. I've not seen nor tried the Poorman's, but if it is not well-flavored, I'd have to wonder if it were the same, since the first four have a rich, sweet, delightful grapefruit taste, almost completely lacking the naringin bitterness of other grapefruit. More like the flavor of a good pummelo, but with the tenderness of the pulp similar to a very mature grapefruit. They tend to be quite early maturing in Florida.

Many years ago, a colleague of mine tried irradiating 'Triumph' seeds, in an attempt to get a seedless form, much as was done with 'Star Ruby'. So when I came to Florida Southern College, we had a dozen or more trees on our campus, as test seedlings. Unfortunately, none of them turned out to be seedless, and some were very poor growers (apparently too much genetic damage). But some were excellent. The freezes of the 1980s did them all in, sorry to say.