This was one of the original criticisms last year when V26 was released. It was said that the mapping detail displayed was reduced at higher scale settings to keep the processing and map refresh speeds up.

In hindsight, I wonder if it was a precursor for the introduction of the 3D perspective mode.

Don't think there is anything you can do about it. You kind of get used to it - I tend to run in nothing greater than 450yds now anyhow - and with the 3D Perspective mode you can 'see' further ahead anyhow.