I am not disagreeing with you and if done correctly by some one that actually knows what he/she is doing you won't hurt it - it being the sheetmetal uni-body. However, there-in lies the root of the problem.
DISCLAIMER: Not trying to ruffle anyones feathers...
Most consumers don't have the equipment or (if they do) the ability to use it correctly. Just because you bought a welder, doesn't make you a welder.
We try to make our installs as simple as possible without having the consumer be a full on fabricator. That's our job, haha.
Bottom line if rosette holes were needed they'd be in the part...
Bob