On PAL UK Gamecubes the Progressive Scan signal was disabled. Although many UK GC's feature the analog and digital outputs. This was to allow most games to carry the 50/60hz signals although on some PAL GC games we didn't get a choice. 50hz o-rama for us UK punters on Luigi's Mansion and Wave Race: Blue Storm for example.
You do need a NTSC GC with a component cable to achieve this.
You do need a NTSC GC with a component cable to achieve this.