I know it's stupid to discuss timelines and canon in games like Pokemon. But I want to know if HGSS and Platinum take place at the same time or not. I want to make two ROM hacks and I want to write a story that connects Legends Arceus to Platinum and Platinum to HGSS. Using the dex expansion I plan to add the hisui forms to HG since its only possible in HG so far and the way I'll justify it is that after doing an event involving Celebi it let's you travel to past Sinjoh and there you can get hisui forms via gifts from Akari