This is both a misspelling and a homotypic synonym. Hymenochaetales: A molecular phylogeny for the hymenochaetoid clade is a widely cited paper that separates Phellinus and Fomitiporia as closely related, but distinct, sister clades. However, on iNaturalist the correct spelling/gender agreement of Phellinus robustus has already been synonymized with Fomitiporia robusta, so this is more of an orthographic swap than anything.