Becore egghead even started he said:
Bonney was kid.
Vegapunk would tell important message to the world.
Dragon was a marine(obviously admiral).
Timeskip which will happen in elbaf.
Franky getting kuma's fruit.
Blackbeard pirates in egghead.
Robin will be kidnapped later on.
It wasn't really hard to surmise that Bonney was a child. Adults don't really refer to their father as "Papa" and "Daddy".
Dragon being a Marine has been a theory for 20+ years.
Elbaf hasn't happened yet.
Franky getting Kuma's fruit has been apart of the Goroawase theory for years.
Blackbeard Pirates going after something on Vegapunk's Island..... Pretty easy assumption to make for them.
Robin will be kidnapped is another theory that's been around for years, and its playing off of Oda liking to restructure preskip scenarios. Also, hasn't happened.
It seems more like to me, that gohdroger scours the internet for theories they find interesting, then writes a vague "Headcannon story" based off of those theories, and some stick and some don't.
I use to write a lot of theories, and for some the premise would be spot on, even though the details would be way out in left field.