RHS terminology: seed [???]/pollen parent

[tropterrarium]

Just stumbled across something odd:
RHS uses the terms "seed parent" and "pollen parent" for the two contributions to a hybrid. Pollen, perfectly fine, but last time I checked, seed is the diploid product of a union of a haploid ovum with a haploid pollen (via pollen tube). So ovum and pollen are parental, while seed is the diploid starting point and is already the hybrid.

Anybody know about this? Is there some historical reason for this inaccurate terminology?