Technical mountain biking for this site is defined as any riding that takes good balance and bike handling skills NO MATTER WHAT SPEED. So for instance if a ride was a piece of cake at slow speeds but very challenging to make corners at high speeds it is still referred to as technically easy.
As far as Blue Diamond, Black Diamond type ratings, those seem to be relative as is the case with ski areas. The black diamond run at Jackson Hole is not the same as the black diamond at
Mount Bachelor . Every town wants to claim a few black diamonds so as not to feel inadequate. If you are new to an area the advice would be to start with something that sounds a bit easier than you would normally do and go from there. Mountain biking does not take the commitment of say a wilderness kayak run. If it is getting too hard for you stop, turn around and go find something else.