I have two different kinds of P.sieboldii. The other one is grown from Barnhaven seeds, and there are different shades. They all flower at the same time, and have foliage which goes underground in August.
The two first pictures are from these Barnhaven P.sieboldii.
The third and fourth picture are of plants which I have gotten from my mother who had gotten them from Estonia maybe 20 years ago. These plants flower about two weeks before Barnhaven P.sieboldii, but they have similar leaves and also this plant goes dormant at the same time in August. None of my other Primula go dormant at this time.
I can't think what other species this earlier flowering plant is, but what do you think?