I get that and you're right with what you say. You fall into the trap of now classing a handheld/console hybrid as both, lumping both markets together, when they used to be separate things. Has the switch sold so well because it's a handheld, a console or a hybrid? Each one gives us an indication on the health of the market.
You're severely oversimplifying the situation.
Nintendo themselves have released numbers concerning who plays in what mode most often.
Unfortunately, this is from Nintendo's six-month financial report for FY 2018, which only covers through the end of September 2017, or the first 7 months of the Switch's life. As far as I know, they never included these numbers in later reports. But here's what we know from it anyway: As of September 2017, 19% of players primarily used docked mode, 30% primarily used handheld, and 51% used a mix. "Primarily" means at least 80% of playtime was in one mode.
Assuming these percentages stayed consistent and that the "mixed" category can be assumed to average out at 50% playtime in both modes, we can assume that roughly 44.5% of playtime is docked, while 55.5% is portable. Considering
the Switch has sold 132.5 million units as of September of this year, that's an estimate of about 60 million "docked" units, and 72.5 million "handheld" units.
All that being said, there are a few anecdotal but extremely likely reasons these assumptions are invalid.
- The aforementioned docked vs. handheld figures are from the beginning of the Switch's life, when having "a home console that you can play on the go" was much more of a novelty that more people wanted to mess around with. I can't speak for anyone else, but I used handheld mode at least 20% of the time back then, and I almost never use it now.
- Aside from Mario Kart, the Switch's biggest games up to September 2017 didn't have much of a couch co-op focus compared to today. No Smash, no Kirby, not even Mario Odyssey with its semi-multiplayer.
- Finally - and I can't stress this enough - the idea that a large number of people who use handheld mode don't care about docked mode - even if they primarily use handheld - is fucking retarded. Yes, the Switch Lite exists. But the fact that it sells so much less than the other Switch models should be a clear indicator that people do care about having it as a home console. The Lite exists for that small subset of people who only want a handheld (or people who want two Switches for whatever reason), the OLED exists for people who play in both docked and handheld (with a likely bias toward handheld), and the normal Switch exists for people who either prefer or exclusively use docked.
Long story short, it's safe to say that Switch playtime is about 50/50 between docked and handheld; coincidentally, that lines up with a
2018 interview with Doug Bowser. If you want to take the braindead approach of assuming that handheld playtime doesn't count toward Switch home console sales, then the "docked sales" still outsell every other Nintendo home console except the Wii, and significantly outsell PS5 and Xbox Series.