How could you possibly know if there is a "very small number of drug cheats?" Do you go around & ask everyone "hey dude...are you using any TRT/HRT?" And what do you think a guy using TRT/HRT is going to say in response? "Yeah, I'm sure am using TRT...thanks for asking." Lol.
Keep in mind that guys using TRT/HRT are going to keep it they're own little secret (imagine that. Lol). Their only concern would be to circumvent any possible testing - if they're even tested at all. And they're are plenty of sites & YT channels that show glow times & clearance rates for various PEDs. With the internet, PED users have so much access to information that they didn't have 30 yrs ago.
Take Dehydroepiandrosterone (DHEA) - a hormone sold OTC as a dietary supplement in the U.S (it costs pennies & there are numerous brands on the market). DHEA, like testosterone, has been shown to decline with age.
One acute oral dose before a HIIT workout was shown in a study with middle-aged men to significantly increase free testosterone & prevent it from declining during high-intensity type training:
https://pubmed.ncbi.nlm.nih.gov/23417481/#:~:text=These%20results%20demonstrate%20acute%20oral,benefits%20related%20to%20HIIT%20adaptation.
Then I found a study from 1998 (Bosy et al) that show a daily oral dose of DHEA taken for 30 days doesn't trip the 4:1 T/E ratio that's needed to test a sample for any HRT use. And I'm a 64 yr old moron with the internet & I could find this info. Lol.
So, let's use DHEA as an example. How could you possibly tell if another runner is using DHEA unless the bottle happens to fall out of his pocket or something? Lol