The other explanation is that unifoliate and bifoliate are not quite as clear cut and black and white as the words suggest. Often enough, a bifoliate will have some unifoliate growths, and vice versa.
If and when you get flowers on both kinds, you will be able to see whether you really do have two different plants.
In the meantime, rejoice, you may have had two for the price of one ! What's to grumble about ?