You say you did your homework, but the dog must have eaten it as you haven't presented it.
ok, here it is for your reading pleasure:
1) cases where a player explained the positive urine sample test via claiming _supplement_ contamination. ITIA/Tribunal/CAS ruled in these cases that a player was 'Not at Significant Fault' therefore allowing for a reduced penalty (full penalty is 24 months for non-intentional use):
Haddad Maia - 10 months suspension
Kamil Majchrzak - 13 months
Demoliner - 3 months
Bellucci - 5 months
Jarry - 11 months
Marcondes - 9 months
Halep - 9 months
Klier - 12 months
Bartunkova - 6 months
Sharapova - 15 months (this case is slightly different since it was not a case of contamination. Buit the penalty is still based on 'player did not intentionally used a prohibited substance, she was not at significant fault, but a fairly substantial fault nonetheless)
seems fairly consistent, anywhere between 3 and 13 months depending on 'how much a player was at fault not making sure that supplements are safe'
2) cases where a player explained the positive urine sample test via claiming _medicine_ contamination. ITIA/Tribunal/CAS ruled in these cases that a player was 'Not at Significant Fault' therefore allowing for a reduced penalty (full penalty is 24 months for non-intentional use):
Swiatek - 1 month (there has not really been a case of contaminated medicine within tennis players, at least not recently. There have been such case involving athletes outside tennis. The 1 month penalty is in line with the reasoning that a player is reasonably expected to assume that medicine is not tainted vs assuming a supplement is not tainted due to more strict regulations around medicine - thus lesser penalty. That has been an accepted 'standard' when doling out penalties. note that for example Verdasco got 2 months for failing the test when he claimed that he just forgot to renew/get his TUE in time. Different circumstances - but a short ban is not unheard of.
3) cases where a player explained the positive urine sample test via claiming _contamination via consuming tainted meal_. ITIA/Tribunal/CAS ruled in these cases that a player was 'Not at Fault' therefore not imposing any penalties:
Moore - no suspension
Gatica - no suspension
4) cases where a player explained the positive urine sample test via claiming _contamination via consuming tainted meal_. ITIA/Tribunal/CAS ruled in these cases that a player was 'at Fault' therefore imposing penalties:
Errani - initially 2 months, then 10 months on appeal.
5) cases where a player explained the positive urine sample test via claiming _contamination via contact with another human_. ITIA/Tribunal/CAS ruled in these cases that a player was 'Not at Fault' therefore not imposing any penalties:
Sinner - contact via a massage, - no suspension
Yastremska - contact via, ahem, you can read on your own, - no suspension
Gasquet - contact via a kiss, - no suspension
Bortolotti - the docs are redacted so it is hard to know what the explanation was. _Because_ it is redacted I would assume it involves another person. - no suspension
there does seem to be a pattern of contaminated supplement -> most at fault to contamination via a human contact -> not at fault, with penalties spread logically depending on the level of fault.
If you want to see a conspiracy, I'm sure you can find it. If you look at it without emotions - makes sense.