>>48070739Unlike HGSS the original GSC only required a single HM, Flash, to get battle Red at Mt. Silver. That HM was also optional if you know what you're doing.
Though it seems pointless to require any HMs at all given that the area is only accessible if you already have 16 badges.
Why did Gamefreak feel the need to increase the number of necessary HMs in HGSS only to cut down on the number of necessary HMs a year later in Gen 5? Gen 5 was less reliant on HMs than Gen 3 and Gen 4.