There are significant safety margins on take-off and landing performance, and on structural reserves. However, there are rarely any significant safety margins on CG.
Whilst you should of course do your damndest never to fly overweight (or at an unknown weight), the basic statement is correct - weight is far less likely to kill you than trim.
I do not dispute that basic statement as a fact.
A generalisation here, but the possibilities go on and on:
Over weight + ramp check = no licence and court case
Over weight + incident = no insurance
Over weight + know it all pilot = accident
Over weight + serious accident = your estate being sued
I know of about half a dozen fatal accidents in the last 30 years or so that I have had some involvement with, that had over weight as a significant factor.
If you are in training and testing, then there can be no compromise.
You fly outside the envelope, you are a test pilot!