I used to think otherwise but not anymore. At stud they're all maidens again.
Chemical enhancement as a racehorse and subsequent siring ability as a stallion are mutually exclusive.
For example, 6 of the top 10 2yo sires & 7 of the top 10 3yo sires in the USA came from the barns of Trainers with multiple positive tests. An enhanced race record might score a potential sire a better group of mares than he might otherwise have gotten but in the end, if he is no good...if he doesn't have what's required...good mares and all, he will still fail.