Not sure where you got that info from but in all the research and reading I’ve done on 3D printing I’ve never come across anywhere saying isopropyl will melt plastic or resin (it’s even bottled and stored in a plastic container!). I’ve lost small parts for months in the bottom of my cleaning tank and pulled them out and other than making a few trips through the spinner at the bottom there is no issue with them being melted. If something got melted then there was other issues with the print, perhaps the resin wasn’t fully cured or the walls were paper thin. I don’t claim to be an expert but I’ve done a fair amount of reading to make sure I don’t have these issues and have yet to have any, or read of any, and I wouldn’t leave parts soaking overnight but 10-20 minutes for sure I do all the time.