If he had acute renal failure he would feel it. He said he felt great, so you have to go with that which would align with chronic renal failure as his body has adapted to the toxins over time. Most don't even know they are at that stage until they have been their a while. Once he starts to lose his appetite or potassium climbs, it's game over.
And it is entirely possible for him to fry himself in 5 years. Grams upon grams of AAS, synthol and maybe a genetic predisposition. With the availability of AAS and the non stop cycles guys run now, this kidney thing will be an epidemic soon. But he's living in denial right now thinking he can just lower the dose and be okay. He would need to come off completely, lose 50 pounds, lower protein drastically, not workout and then hope for the best.
If your kidneys are failing you feel like shit period. The body doesn't really "adapt" to the electrolyte imbalances, fluid overload, azotemia, and everything else that comes with it - be it stemming from an acute kidney injury or chronic progression of renal disease. I don't really expect Bostin to be forthright about how he's feeling, so speculating on that is dumb
Is it possible to develop chronic kidney disease in 5 years? Maybe but it's unlikely .. assuming the labs posted above are actually his, it's far more likely that the high BUN/creatinine is from some type of AKI.
Anythings possible though