Since January's Georgia Senate runoffs, which ensured a Democratic majority, U.S. cannabis stocks have seen a series of peaks and troughs as investors await industry friendly legislation and more institutional backing. Though many U.S. cannabis companies posted strong fiscal fourth-quarter earnings, "the bar was set pretty high," Tim Seymour, portfolio manager of the Amplify Seymour Cannabis ETF (CNBS), told CNBC's "ETF Edge" on Wednesday. As such, those who compared results to the prior quarter were left disappointed. But year over year, these companies have made significant strides, Seymour said, noting that Green Thumb Industries doubled its 2019 volume in 2020.