I was thinking about this article over the weekend as I biked to a race (not commuting, but still bike for transport) - I'm one less bike commuter since I work a home office. I didn't see the article address what appears to be a growing trend of people working from home. IMHO the bike-commuter is the kinda person that values a work-from-home arrangement more than the average person and that will reduce the number of bike-commuters.
Also, it appears they are using the same survey methodology for year-over-year comparison. However, with bike commuters being a small number of commuters, a small shift in the survey base can result in a large shift in the bike-commuter numbers. I honestly think it's a weak methodology. We need to combine a variety of methodologies to get more accurate results (i.e. Strava & other sports tracking apps, human & automated counters on busy bike routes, along with the surveys).