There were a number of gaps in the testing in the McLaren report. That was in part why the numbers were so big. In biathlon there was a significant number, and some of them were listed with question marks or notes - Romanova had a couple which were simply marked "scratched sample" and there was one for somebody else, my memory is saying Zaitseva, but probably more likely Vilukhina as she was one of the two that got suspensions straight away from the report data, which had a salt reading beyond the realm of human possibility, so it was known that it had to have been tampered.I thought I read somewhere that this decision does not base solely on Mclaren report, but to the fact that WADA has found concrete evidence that the Rusada files they collected (after admitted one month later than the deadline) had hundreds of test result either missing/deleted or the data was manipulated. If the data would've been clean, this decision would've probably not taken place. As far as I've understood.
How they concretely decide who can compete under ANA and who not is of course mystery and interesting legal challenge for sure.
At the same time, the numbers were inflated somewhat in a few other ways. I've mentioned before that there were 12 athletes who appeared in the files solely because they were subjected to one test on one particular date in Sochi at a training camp for the junior team, 11 of whom came back clean and one of whom had no result logged. Evidence of tampering? A sample gone missing? Or just an error of logging? Or a dry run for how to make a sample disappear when the big guns came in a few months later? Just too hard to tell, but there was really nothing that suggested anything against any of those athletes. And IOC clearly agreed, since Kaisheva was one of them and she was one of the four Russian biathletes who was cleared to compete at Pyeongchang. So was Latypov, though his later meldonium positive - even though that was then quashed as it turned out the substance had been banned before they knew enough about it, and its long half-life led to a number of false positives, contested cases and similar fiascos - will probably prevent him from any further competition as an ANA if the ban is upheld. Some of the others that have made it onto the World Cup since were also part of that group. You'd think they'd stand a good chance of appearing as an ANA if Kaisheva was cleared and they've been competing at international level for the last few years too - Eliseev, Povarnitsyn, Mironova and Pavlova would have been in the junior age groups that year too - but we will probably be saying goodbye to Malyshko, Garanichev and their generation, plus almost certainly Loginov, Starykh and Glazyrina.