Article referenced above covers only processing of data from satellites.
As far as it went, Easyjet announcement referred only to data from (a) camera(s) on board aircraft.
Intuitively, it seems more likely that you'll get good data from a near-vertical shot down through the atmosphere than from a horizontal one. For a start, if there is VA in a horizontal shot, the camera will be looking at the cloud edge-on - that's not going to give data that's easily processed to extract (eg) density information. A vertical shot through the atmosphere down to surface will have fewer datapoints than a horizontal shot of indeterminate distance.
Also, this idea of $$$ and kilos of on-board processing to give VA information to the captain of one aircraft seems crazy! Much smarter to transmit the raw data to ground, where it can be integrated with data from other aircraft, satellites, etc. and presented directly to ATC in the relevant area(s). I don't understand at all the philosophy of individual aircraft seeking their own way around (under, over,?) VA clouds. Recipe for total chaos.