Yes...he is. Schumacher is providing expert testimony on the performance benefits of EPO in a CAS hearing involving an elite athlete:
Karamasheva Cas hearing (2017/0/5268)
Paragraph 77: EPO "can increase oxygen supply by 6% and take as much as one minute off the time taken to run 10,000 meters, and proportionately more over lesser distances."
CAS says Svetlana Karamasheva is a Russian middle-distance runner at the international-level. Her PB is 3:59.61. Now if you want to argue that she isn't an elite athlete because her PB isn't fast enough or something like that - then go ahead but you'll be laughed off this thread. Otherwise, if you concur that she's an elite athlete, then you need to understand that Schumacher is stating the performance benefit observed with EPO in an elite athlete's CAS hearing.
Irreverent since Schumacher is providing expert testimony. The arbitrator didn't ask if his testimony is "peer-reviewed" - the arbitrator wants to know if EPO provides a performance benefit with elite athletes. Again, I remind you this case is involving an elite athlete, not sub-elite, well-trained, recreational athlete, etc.
You're correct - it wouldn't have anything to do with the verdict. However, it helps with the "unfair advantage" clause when times, awards, medals, titles, etc. are going to be annulled over the time period of the hematological anomalies detected on the passport - particularly at or near key competitions. Let's take a look at the language in the disqualification summary from another CAS hearing involving a Russian doping case:
Ugarova CAS hearing (CAS 2016/0/4463):
"141. The Sole Arbitrator does not deem it appropriate to entirely dispose of any disqualification of results as he is convinced that the Athlete doped and because the main purpose of disqualification of results is not to punish the transgressor, but rather to correct any unfair advantage and remove any tainted performances from the record (LEWIS / TAYLOR (Eds.), Sport: Law and Practice, 2014, para. C.162, with further references). The Sole Arbitrator, considering that neither a doping scheme, nor a doping plan has been established in the present case, deems it adequate and proportionate comparing to other cases where a single anti-doping rule violation could have been established through the analysis of a positive sample, to disqualify the results of the Athlete for a period of six months. Six months seem to be a period long enough for an anti-doping organization to perform results management including a possibledisciplinary proceeding."
I take this to be that the ban (e.g., 2 yrs, 4yrs, 8 yrs, etc.) is punishment for the breaking the rules of doping while the disqualification of results is to correct any "unfair advantage and remove tainted performances" from the performance benefit of doping (i.e., elevated hemoglobin from a prohibited substance or prohibited method in ABP-hematological anomalies cases).
"Unfair advantage" would equal a performance benefit over presumably the undoped competition.