All teams still do regular testing themselves. It's in their own self-interest to continue the testing to mitigate the risk of an outbreak within the entire team.
I also disagree that the new UCI protocol only obliges "really sick" riders to disappear from the race. If a rider tests positive by means of a PCR test, a medical panel - consisting of the doctor of the involved team, a doctor of the UCI and the designated doctor of the TDF - will decide on possible isolation. They will take into consideration the relevant clinical elements. If the viral load is high enough to risk infection of other riders or if the rider’s own health is at stake, he will not be allowed to continue.
To be clear, such decision was not made yesterday because all tests were negative. Contrary to what you write, it seems that teams have not let riders who tested positive continue to ride.
I am also surprised that Guillaume Martin allegedly said that he would not have been required to leave if the UCI protocol was applied. He can’t possibly know what the panel of doctors would have decided in his case. Moreover, he has been sent home by his team, so in consultation with the team doctor. That same doctor would have been involved in the UCI panel decision, so it's unlikely that the decision based on the UCI protocol would have been any different.