Vortex Fury HCD only works if less than 15 degrees angle ?????

[v8rider]

Reading the Vortex fury manual it says it's not for angles greater that 15 degrees at 800 yards or 15 - 30 degrees out to 400 yrds. I have not see other (mid - high end) Bino / Range manufacturers mention a limitation on the angle it can be used. Majority of my mountain shots are greater that 15 degrees, although I don't typically shoot past 600yrds I'd like to be able to trust my Rangerfinder if I was going to!