Yes Richard would you please explain that, I have never heard that either and I do just the opposite alum on auto, wooden on manual.
Aluminum frames weigh a pound less than wooden frames.
Properly made modern frames support the mesh the same as aluminum.
In the early 1980's I did lots of measuring experiments with weights to determine the strength of aluminum and wood members for frames and found the deflection to be the same. As I was stretching my own mesh on the frames, I found the most important factor to be pre-bowing the frame in the stretching equipment. If you didn't, when the mesh is released and all the force supported by the frame, you lost 4-6 newtons instantly.
The real lesson is that all frames are stronger than the mesh and when you lose tension, IT IS BECAUSE THE THREADS HAVE ELONGATED as they relax or are stretched by the squeegee during printing.
I turns out that squeegee strokes align the polyester fibers and used mesh is actually stronger than virgin mesh, fresh off the bolt. Loss of tension has nothing to do with the frame.
I started buying 12 Newman Roller Frames per week, until I reached 600. I was able to print more opaque, thinner deposit of white ink, through a higher mesh at twice the speed at 30 to 40 newtons.
If you have an automatic, buy wood, but if you have a manual press, buy aluminum
On a six color job, that's 6 pounds less to spin and stop, for each color. A gallon of milk weighs about 8 pounds. An auto has no trouble lifting the extra weight 600 times an hour and the heads don't spin.