This was thought to be a proposed name for the porcini that comes up in the Sierra Nevada mountain in the spring. The similar name, Boletus rex-veris, has now been formally published. This taxon is clearly distinct from the European Boletus edulis and there genetic evidence to support this distinction. These have been called Boletus pinophilus by some since they are associated with pines. But that is a European species that is very close to the European Boletus edulis. See Fungi of Switzerland Vol. 3 for a photo of B. pinophilus which doesn’t look much like the spring Sierran porcini.
Some of the distinctive characteristics of the B. rex-veris are a pinkish tone to the cap, the whitish blush when young, and the tendancy to fruit in small clusters.
According to Dimitar, this was finally published in late 2008 as a separate species in the journal of Economic Botany in the article “California Porcini: Three New Taxa, Observations on Their Harvest, and the Tragedy of No Commons” by Arora and Simonini. I’ll provide more details as I get them.