Very good question.
None of you seems to understand that offering an explanation that is consistent with the known facts is not the same as saying that explanation is definitely what happened, nor does it rule out the possibility that both that explanation and another one might simultaneously be true.
When it comes to passport irregularities, it’s almost always the case that more than one scenario is consistent with the data. UKAD apparently leaned towards the idea that JTL took EPO some time before the passport sample was withdrawn. Maybe he took it in conjunction with a transfusion, in order to keep his retics up, and they subsequently declined when he stopped taking EPO but had a high and retic-suppressive HT. Or maybe he just took EPO, and as Cat notes, his retics declined following cessation of the EPO.
I haven’t read the report, but AFAIK, there is no evidence against the alternative possibility that he transfused just prior to the Worlds. It’s pretty hard to argue that the only possible explanation for a very low value of retics at some point in time is a manipulation 10-14 days earlier. In fact, based on the studies I've seen, I question whether a massive decline in retics occurs following cessation of EPO. Typically, when you give a subject EPO, retics spike followed by a slower, more sustained rise in HT, followed by a fall in retics. But the retics don't necessarily fall below their original level, at least not within two weeks. E.g, check out Figure 2 in
this article. I really am not seeing how a very low retic level is a very strong indicator of EPO use rather than blood transfusion.
So why did they conclude it was EPO earlier and not a blood bag later? It doesn't seem that this conclusion could be based on any scientific evidence. Maybe they thought transfusion would be too costly or inconvenient for him. Or maybe, this is a cynical view, they wanted to nail him for the TOB as well as the Worlds.