Note that in two seconds the actual VS had changed from 500 fpm up to a like number down. That is remarkable, ...
The change corresponds to a normal acceleration of 0.85 g, well within the ICAO “light” turbulence criterion of 0.5 g peak to peak. (3.5 seconds of normal acceleration of 0.85 g changes V/S downwards by 1000 fpm.)
Have you a reference for the deflection of Vanes due airmass
The vanes are shown on the same page 42 as AoA IRS1,2,3.