I'd love to see where you saw this, LOL. In the Kabam tutorial? I think not.
From the game when you click on support link put in search "drop rate". Check out the "drop rate issue". Support link located in settings. Same place where is the link to sign up for the forum. And yeah, surprisingly Kabam has tutorials. Some kinda:) That's why the guys doing great thing by putting up info together.
Wait.. you're talking about this?
Sorry, but you are grossly misinterpreting what this says. It does not say "drop rates are fixed to drop bots in sequential order". It says drop rates are what they are so that no one player gets a better chance over another player buying the same item/crystal, etc.
Now I'm sure someone is gonna show up and say "well, Kabam knows how to fix the drop rates because the 1* bots drop in order of the ones you currently do not have."
This has only ever been observed of the 1* bots. No one has been able to show the same level of drop rate control with any other tier bots.
If this was true of all the other tier bots, no one would get a duplicate until they had the entire bot roster in each tier.