Hi Paul and Duane,
My impression is that colocation of the vantage points and the root servers in a data center is a corner case the vantage point operator will have to address. I am not sure it is necessary we indicate how this should be treated here, and simply raising this might be sufficient - without going into the solution space. I am not able to say whether these measurements are representative or not and also suspect it depends on the other vantage points. I would propose maybe something around the following lines.
OLD:
"""
Vantage points may be deployed on “bare metal” or virtual machines (VMs). When VMs are utilized, they should provide dedicated IP addresses and a dedicated operating system environment.
"""
NEW:
"""
Measurement that result from a colocation of vantage points and root servers in a data center needs to be appropriately treated in order to make the measurement representative.
"""