original forms of the trio of creation

I was browsing some posts here on Reddit and saw a lot of people saying that Palkia's original form, unlike its sister Dialga, was just a copy of Arceus because, like Giratina, it's jealous of Arceus. Is this true, or am I just seeing people spreading misinformation?
Because whenever I stopped to look at the original forms of Palkia, Dialga, and Giratina, I saw them as the same thing, and I never stopped to consider that any of them were just copies, because then it wouldn't be an "original form."