Are all EDTAs the same?

[Rapayich]

Hi,

I am making my own fertiliser solution. In doing so, I am considering multiple different brands of EDTA Copper, Zn and Manganese.

However, I notice discrepancies in the stable ph ranges of the same EDTA nutrient. For example:

Brand A EDTA Copper is stable between pH 1 - 10
Brand B EDTA Copper is stable between pH 4 - 8

Is the wider ph stability of Brand A a marketing tactic or a legitimate figure? In my head they are both EDTA copper so should be stable in exactly the same ph ranges. Possibly Brand A is stating the stability range in which there is still some chelation and brand B is stating the pH range in which there is full chelation?

Thanks