For anyone reading who is unsure of how the test was conducted, Squirty built a multi-tiered lazy susan and secured the Wii U Gamepad, the Switch Pro Controller, and the Joycon Grip to each tier. This configuration allowed him to move controllers for each console with the same degree of rotation and at the same speed and velocity while playing the Splatoon 2 test fire and Splatoon 1 live simultaneously. He changed the sensitivity of each game between to see how the settings correlated.
I'm sure he'll want to be more thorough in reviewing footage before publishing his results (he did spend a year testing Smash, after all), but some of his preliminary findings were as follows (please bear in mind that I'm summarizing in my own words what he shared on our team discord server and am taking some liberties with inferences based on what he said):
-There is nothing inherently wrong with how the Switch handles Gyro. There is no evidence to suggest that the Splatoon 2 demo attempts to take any shortcuts or overcompensate in any way that is more aggressive than Splatoon 1.
-Sensitivity scaling (or perhaps just the default point of reference) is different between the two games. Anecdotally, the closest correlation he could find immediately following the test was between +5.0 sensitivity on the Switch and -0.5 on the Wii U. Take this information with a grain of a salt, because there are probably some factors that can't be accounted for, like the placement of the accelerometers in each controller and how their distances from the point of rotation might affect results or how off-center placement of the accelerometers (which is almost certainly the case in the Joycon Grip) might similarly affect results. The takeaway therefore should not be that -0.5 = 5.0 from Wii U to Switch, but just that there is a noticeable difference.
-Adjustments will need to be made when learning to play on the Switch. We're not going to get a 1:1 ratio that allows us to transfer our muscle memory informed by hundreds to thousands of hours of gameplay seamlessly from one game to the other. We basically already knew this given the change in size, weight, and shape between controllers, but testing suggests that there will be other factors that add to the learning curve.
-The Switch will handle subtleties in motion control better than the Wii U. Squirty described the Switch's response as "less confused" than the Wii U's when doing things like slowly rotating and coming to a stop.
-Drift correction is least aggressive on the Switch Pro Controller among the three configurations tested. This is a good thing for any Switch owners who might have been worried they'd have to bench their $70 USD investment.
tl;dr version: Switch has a lot of upside, but a lot of people will experience growing pains while adjusting to Splatoon 2.
I look forward to Squirty politely letting me know I'm an idiot and that I've completely misrepresented what he said. :p