Until a biplane is trimmed out properly, a lot of them tend to jump off the ground very quickly and can be pointed straight up if you're not quick on the sticks. Someone not ready for that or with low stick time can easily over-control or mis-control and put it right back in the ground.

Even though I can fly pretty much anything, unless the model is a simple stick or trainer type, I usually let a better pilot do my test flights just because he doesn't have the hours invested in the build and will be calmer about it than I will. Plus my test pilot flies every week and I sometimes go years between trips to the field and many times when I make it back to the field it's with new planes.