Bonds and Williams especially don't look particularly different to me.
Bonds averaged 37 HR per 162 games until 2000, when he went to 55.5 HR in his 35 yo year.
Aaron averaged 38 HR per 162 games until 1971 (37 yo) when he went to 54.7.
Mays averaged 40 HR per 162 games until 1965 (34 yo) when he went to 53.65.
Ted W. averaged 38 HR per 162 games until 1957. (38 yo) when he went to 46.63.
There was nothing extraordinary about an already generational talent like Bonds's 2000 season.
Huh? I read this at first as a comparison of their 162-game averages before and after X year—only later realized you're comparing the entirety of their careers prior to X year with that single, cherry-picked outlier year. For straight up comparison of their 162-game average HRs before and after your chosen years, B-Ref gives the following:
(and, NB, this is including the outlier years on the "after" side, in maximum fairness to your argument)
Bonds: 37 HR/yr until 2000,
52 HR/yr after
Aaron: 38 HR/yr until 1971, 37 HR/yr after
Mays: 40 HR/yr until 1965, 30 HR/yr after
Ted W.: 38 HR/yr until 1957, 36 HR/yr after
Any one of those seem unlike the others?
And note again this is using 162-game average—if we used actual HR averages per season the difference would be even more extreme (Bonds 32 HR/yr >
40/yr, Aaron 35/yr > 27yr, Mays 35/yr > 23/yr, Williams 28/yr > 26/yr).
I feel like this has turned into a relatively minor discussion about whether Bonds' 2000 year should count on one side or the other of the boundary where his numbers clearly went through the stratosphere, rather than the original question about whether his late-career surge bears some relation to the claims that he started using PEDs sometime after 1998. I'll happily grant you the point about whether the numbers started going up atypically in 1999, or if it was 2000, or 2001, or whether the upturn was quite so pronounced at the beginning, or rather flatter in the first few years and only more extreme later, etc. etc. etc.—the broader point remains the same.
Edit: Savin Hillbilly beat me to the gist of much of this.