They don't realize it because it probably isn't true. He has a starters arsenal, his K rate and BB rate looked good deeper into games. He just gave up a couple more HR than you'd like which isn't a huge surprise when you are in the process of being stretched out. Nothing he has done suggests he is a RP at this point. You can make that case with Peralta if you ignore what he has done this offseason since Peralta actually has a RP arsenal, but Houser throws I think its 5 different pitches, no reason he can't be a starter. People have just latched onto he is a RP because of like a 10 IP sample while being stretched out having a bad ERA. His xFIP as a starter last year was 3.71 and it was a 3.31 as a RP.