Those who are arguing that you cannot tell how suspicious a rider is based on performance need to think about it for a second.
Yes, its true it is difficult to judge a riders suspicion just by looking at progression if that progression is steady.
However Riisesque progressions do heavily imply doping because it is simply unnatural for someone's physical capabilities to change overnight in mid or late 20's.
Same way its unnatural for someone who is 1m 70 at the age of 18 and 1m 71 at the age of 25 to suddenly measure 1m 95 in height a year later.
The analogy i would use is lying in a police interview. If someone is caught lying to the police in an investigation that heavily increases their chances that they commited some crime.
But does telling the truth make someone 100% innocent?
No it doesn't.
And in the same way moderate improvements do not make someone 100% innocent eg Nibali, but rapid overnight ones, DO heavily imply something isnt right.
Its possible that someone is lying but innocent and its possible that someone had sudden late improvements without doping. In both cases however it is very rare and takes rather extraordinary stories and background to explain it.
Funnily, Sky claim to through pure extraordinary coincidence to have just chanced upon those 3, "1 in a million" guys who have those late improvements naturally, and all have their own extraordinary stories and reasons behind it.