Thanks for this. The issue seems to be tests can't be conducted frequently enough at the right times of day to return an adverse finding. This is mentioned by the Sunweb manager.The best semi recent (2019) article I've read about the state of play: https://www.cyclingnews.com/features/biological-passport-have-dopers-found-ways-to-beat-it/
The other thing about the ABP that many fans (including here) don't seem to understand is the ABP doesn't detect substances. It only measures changes in reticulocyte levels (new red blood cells). So saying the peloton has discovered a new undetectable drug misses the point.
To boost performance you need to boost the amount of RBCs because that is how the body transports oxygen from the lungs to the legs. Hence use of any new drug can be detected as a change in the blood profile no matter if the substance itself isn't detectable. So EPO micro dosing can be used to hide the spikes when blood is withdrawn and reinfused before important races. But it all comes back to testing frequency and timing.