OK, so the whole Trichocereus/Echinopsis/Lobivia nomenclature is currently a huge mess because about a decade or so back they decided it was good to merge them all into one large genus: the genus Echinopsis. At that time AFAIK Trichocereus grandiflorus became Echinopsis huascha. Then a few years back some more taxonomic/genetic research showed that if they wanted to do this they effectively should make most of the South American cacti part of that genus, which people felt was too much, so it was decided to split Echinopsis up again, with another round of renaming the different plants, and of course some additional reorganizing. The Catalog of Life, which this site follows is not up to date on that.
However, this is one of the few original Trichocereus plants that actually had red flowers in nature, whereas most Trichocereus species have white flowers. Because of its flower color and general size it became a much hybridized plant, most of which are sold under the name 'Trichocereus grandiflorus', this is mainly a trick by Altman's to sell the plants, because everyone would agree that the name Trichocereus grandiflorus sounds much better than Echinopsis huascha. 'Grandiflorus' is not a cultivar name, so Baja is correct, this plant should not be under the entry for Echinopsis huascha, but should be under the entry Echinopsis sp. - the generic Echinopsis entry, or if there is a Echinopsis huascha hybrid entry, it should be under that.
Once again: grandiflorus is an old defunct species name, not a cultivar name. A true Echinopsis huascha (aka Trichocereus grandiflorus, see below) would afaik have red flowers, not white ones.
