We will never know until she is busted.
They rarely catch them with tests so they use a bloodpassport. However if you stay 'on' your blood profile starts to look normal.
I'm a cyclist, been on for over a year and my last bloodwork had me inline with the blood guidelines. By all accounts, I looked clean. However on the bike I would demolish the 'natural' me.
They have caught people coming 'off' because the blood changes. A year ago a sky guy got popped and it was from coming off.
So I think that's what Sky figured out ahead of other teams. Stay on = clean. Hell their Leader is from track cycling, the dirtiest cycling there is. But they also have a budget twice as large as other teams so yeah, their talent is pretty damn good also.