Was watching the gaming historian on youtube, he brought up nintendo power with a CVIII walkthrough. I paused on the game description, and the first sentence read "In Castlevania III, you play the role of Trevor Belmont, youthful hero and originator of the Belmont warlord line."
I know NP isn't the greatest official source or anything, but going by this Trevor was the first Belmont to fight Drac, which obviously fits with Iga's timeline. What makes this more significant is the date, which would've been around the time CV3 came out. So the CV1 manual confirms Chris before Simon, and this can be used to show Trevor was the first, therefore before Chris.
I do have to say, I believe the typo at the beginning really was a mistake based on miscommunication, and that they might've intended for the game to either be about Chris originally but the GB devs were like "No", or they didn't know about Chris and made up Ralph/Trevor so they could make a prequel. The C could be a coincidence, but I believe it was put there later, possibly after they changed him from Chris to Raplh or from when they might've originally written him as Chris. Something else we can use to show it was a mistake was how the English verison doesn't even mention "100 or so years" before Simon, so when they were translating and changing the game for the US and PAL releases it was changed.