Vent--
What you say makes some sense, if it can be believed that the 20.19 (+1.2) did not reflect his absolute 200m ability.
However, that 20.28 (-1.3) adjusts to only 20.18
Garry Hill can say whatever he wants, but the proof is in the results. Given the choice, I will take real results to the bank before I take whatever Hill says to the bank.
That result, as well as his 20.19 (+1.2) which adjusts to 20.26, would still compare favorably with Mahorn, whose 20.17 (+0.4) adjusts to 20.20
I think my analysis is still reasonable.
Regarding this "reflection of true ability" concept...there is absolute potential ability, and there is performance. It is fun to discuss absolute potential ability, but not very instructive for certain purposes. 20.28 (-1.3) reflected Wariner's true ability to perform, in that round, in that series of races.
Because Wariner has run plenty of other 200's, both before and since, and has never really come close to that time, although he has had plenty of other opportunities, including in many one-off 200m races, I think it also represents his true ability, regardless of what someone else's belief or fantasy might suggest. His 200m career was long enough, and varied enough, that we have seen what he can do. Look at the IAAF page for his 200m progression.