I believe the problem has been noted in 3.4 as well. But there were other changes to 3.5 that may have made it more manifested.
If you would want to install the latest beta (3.6-dev) from ardupilot master the EKF updates are in there. I simply pulled them out of ardupilot master and merged with my ArduHeli master branch so I could fly the latest EKF code on 3.5.3 in my helicopters. I found the problem to be quite pronounced at higher flight speeds >20 m/s, with the EKF altitude estimator off by 17 meters on one flight. The problem has not re-occurred flying Paul’s updates.