Aigenga,
Halcro, get yourself either a single purpose turntable wall shelf (like the Solid Steel that I use) and spike the turntable to it, or a good stand and an isolation pad like an SRA or Symposium. I would put my naked TT-101 against any plinthed DD and be sure of a favorable outcome.
You're right of course and this is indeed a recommended method IF one has a dedicated rigid wall shelf like yours.
The problem occurs in a situation like mine where the shelf is shared and not dedicated...or where the shelf is heavily loaded because of the mass of the armpods (again like mine).
Mass-loading a shelf induces stresses within the shelf strata and these stresses (mainly the tensile ones) induce low-frequency 'noise' or vibrations in the shelf material.
A massive plinth can help absorb these vibrations without itself resonating especially if the plinth is mounted on slightly resilient feet.
A very low-mass plinth (like my steel cradle) is easier to precipitate into its resonant frequency and steel spikes do little to hinder this.
Most turntable manufacturers are aware of this structural feedback issue and attempt to combat it in various ways like mass, sprung suspension, air isolation feet etc. Rega believes a low-mass plinth (or even skeletal) is best when mounted on compliant rubber feet.
This structural feedback issue is so important that Mark Doehmann has designed his new turntable with a Minus K stand inbuilt into the plinth.
At any rate, I have been doing a lot of testing lately and, because I can do nothing about my shared shelf and its mass loading....I need to try and devise a solution to creating 'mass' for my cradle situation...πβοΈ
A tricky problem....