So I have taken a closer look into this to check if there is ANY way to get this platinum with this save in a legit looking way and I can 100% say, no fucking way.
First of all, again thanks for this amazing save you've surely pumped tons of hours into this my respect.
To get back to my topic, my idea was to get the trophies out of the way bit by bit by doing certain actions. I started with playing one flashback level to ONLY trigger "Closing the Experiment Log". And then doing other stuff but the journey to a legit list ends at this very first step. By finishing ONE level, no matter how, you will unlock ALL trophies with the samr time stamp. You even get the platinum relic speedrun trophy even if you haven't done a speedrun :-/. Perfectionist, All gems etc.. everything pops right away.
The only thing you can like control yourself is "over-achiever" and "over over achiever" since you can decide when you watch the outro.
The only way to get a complete looking legit looking list with this save is to do everything legit on your own and use this save for like a joker. For the speedruns for example but this would mean that you need to do ALL gem related trophies on your own. That's really a bummer.
This would be the perfect save if just one simple gem in any world would be open.
I just wanted to share this information with you. If you don't care about messy stamps, you can get the platinum with this save in no time. Maybe someone out there has a save with some gems left?
Cheers!