Watches vs phone step counts [OC]

I've had three watches over the last 4.5 years and I've logged my daily step counts from the watches as well as from my phone (as tracked by Google Fit). I excluded about a dozen days due to anomalies, mainly days where I'd go for a run and leavey phone at home. The stats were run on the daily data but the chart is weekly to get rid of some of the daily noise to see the relationships better. I forced the linear regression to have an intercept of zero for easier comparison. All watches counted more steps than my phone which largely makes sense since there still might be short periods of time where I put my phone down while I'm in the house. Fitbit was the most off, counting almost 20% more steps than my phone.