This is a good post, and you might be right. But note that USADA states:
If this is true—and we will have to wait to see how true it is—then they don’t need the pre-2004 evidence to corroborate. In fact, I think you have it backwards here. Your interpretation is that they need the pre-2004 evidence to make their case for 2004 and beyond. But if they have “substantial evidence” for 2004 and beyond, they don’t need it.
Then why do they mention it as corroborating evidence? In the letter, they put it the other way round, that pursuing the case for 2004 and beyond will allow them to bring in earlier evidence:
IOW, they will be allowed to use earlier evidence because it corroborates, not, as you imply, that they will be able to corroborate because they are allowed to use the earlier evidence. I think they are trying to use its relevance as a way of being able to extend the SOL. And they need some trick like this, because I agree with you that they may have trouble using the Hellebuyck precedent to get sanctions for pre-2004. But they don’t need the precedent to use the earlier evidence to add to the 2004 and beyond evidence. They are allowed to do that, at least they claim they can (lawyers feel free to step in here), regardless of the Hellebuyck decision.
By the way, given how crucial SOL is playing here, why did they wait for the federal investigation to play out before beginning their own? They could have written this letter, I’m pretty sure, a year ago, bringing 2003 within the SOL. I understand they wanted the fed investigation to finish first, but they must have realized the possibility that it would end up with no charges brought, and thus wasting one year of possible sanctions.