Agreed. Internal testing / external labs doing testing teaches / allows riders to stay under the radar. Clean ABP = perception of clean rider. All the team managers have to sell is "we look clean", and demand the team be clean, preferably via the media.
The riders themselves can go off on their own and do what they want, so long as they pass the ABP "clean" test.
When they don't
eg 1: Millar's 2007 November values and 2008 Tour values looking dodgy - the team manager can trot out something like, "David Millar does not experience plasma expansion because he is not a 'GT' rider, and does not recover, whereas CVV is and does". Even though JV forces Millar to ride the Giro, the Tour and the Vuelta, in 2009, and Millar wins the final TT at the Vuelta.
eg 2: Ryder Hesjedal's pre-Giro values are high, JV says everyone tested high, but provides no further proof, even though there are 8 more riders in that Giro for whom he has access to data.
eg 3: Ryder's last day blood values make no sense, with a 27% increase in retics, and JV starts with "hypoxia induced during the TT", and finishes with, "the morning sample was not stored properly". In the middle he tries to steer the conversation to subjective opinion by saying "If I thought the profile was dodgy I would just fire the rider, I wouldn't release the profile". He also threw in the Clenbutador argument, "retics don't enhance performance, so who cares if they are high?"