@Fueling Around ground venison with formed jerky where all the seasoning staysbin meat, is completely different from soaked whole muscle where meat has to uptake seasoning. He didn't say which he was doing, but I am assuming whole muscle.
You're right for sure, leaving anything too long in any gradient brine will oversalt. And different water will result in different salt and sugar transfer rates. But the whole thing is a complete crapshoot anyways when doing a gradient brine like that, it all depends on concentration and timing, thichness of the meat slices... without any instructions for all three of those, it's just a guess either way. He doesn't have good instructions for any if those 3, So I'd rather use less seasoning with less water, so I'm not wasting much.
Without making it several times so you can figure out your results and tastes, high concentrate gradient brines on unknown meat thickness is again just a complete shot in the dark for results, first few times. Like happened to you, you end up giving away stuff too salty, etc.
For those reasons, I am not a fan of gradient brining on anything. I do equilibrium brine on everything, calculating exactly what my final salt etc content will be, and knowing precisely what my repeatable results will be.