Trevor Reed says that is the case, but he only offers a sample of two Americans (himself and Griner). He says that Russians would "usually receive a year, two years maybe" for the same offenses while 9 years, he says, was unheard of "the entire time I was there". Is this is a valid conclusion in a wider sample, i.e. do Americans sentenced in Russia typically get 9 years in prison for offenses that local Russians typically only get one year?
According to the official statistics (report №10.3.1) published by the Judicial Department at the Supreme Court of the Russian Federation, the claim is only partially correct in Reed's case, and might be partially correct in Griner's.
According to these reports, during the 2016–2020 period, there were no prison sentences over 8 years under Article 318 part 2 (the one Reed was charged with). Thus, Reed's sentence of 9 years was exceptional. A regular sentence under that article would rather be 2 to 5 years, with longer sentences being rarer, but not nonexistent (for example in 2020, 117 sentences were within Reed's "one to two years" bracket, 163 were in the 2–5 years bracket and 5 were between 5 and 8 years). These sentences are often complemented with an additional suspended sentence, but since the reports include only the duration of unsuspended sentences, it isn't clear how this affects the total time of punishment. Note that Reed's own case is not included in the report since it was still undergoing appeals when the exchange happened.
Griner's case is a bit more complex, as she is charged with two separate articles (228.1 part 1 "Storage" and 229.1 part 2 "Contraband"). The Russian Сriminal Code states in Article 69 that for these articles the sentences will be added up as they are considered "severe" (Article 15). It isn't clear to me if these would be listed as separate entries in the reports (i.e. whether the main charge and additional charges are separate entries or whether the listed entry will show the combined time of the main charge sentence plus the time from additional charges). The reports for 2020 have the longest sentence bracket for Article 229.1 part 2 as 3–5 years (15 out of 27). For 228.1 part 1, the largest proportion of sentences is between 3 and 5 years (909 out of 2177), and there were 36 sentences between 5 and 8 years. If these are separate, then Griner's case is a bit higher than average, but not exceptional; otherwise, it is again harsher than maximum recorded sentence. In any case, for either charge, it is not common for Russians to get less than 3 years of prison under these articles.
P.S. The official tables are large, hard to read and hard to search. They also are only available in Russian. I used a free third-party site using that dataset for my search, which also has an English version although I cannot attest for the quality of the English translation.