Would an Isolation TT platform further improve my TT?

You guys sometime make me want to pull out whatever hair I have left. You are spending someone else money without analyzing the situation.
The TT is sitting on a heavy stand on a concrete floor. There is no isolation platform that is better than four inches of concrete and there is no isolation platform that will help in case of an earthquake! If you are more worried about isolation then get a SOTA or an SME or a Basis. Those turntables do not care what you put them on. 
Luxmanc138 spend your money on another cartridge or more music or taking the wife out. Buy her some flowers. Your turntable is just fine where it is. Don't fix problems that do not exist.

I already explained that the building and everything in it - including the cement slab - are vibrating right along with the Earth crust motion, at frequencies between 0 Hz and 20 Hz and higher. The peak frequency of Earth crust motion is around 1-3 Hz. Now, I’ll grant you, that cement slabs are not very affected by rotational forces.

And, the seismic vibrations traveling across the Earth's crust are, Max Townshend claims, many times greater in microns than is the distance a tweeter travels when reproducing a not-that-high a frequency. As are the vibrations that swamp the squiggles in the LP groove the cartridge is attempting to measure.

Not to be too picky ⛏ but it’s actually that the Earth’s crust is moving like a wave, that’s what produces the *very low frequency* up and down movement of the building, and the horizontal movement of the building and the rotational forces that try to rotate and twist the building. It’s just like someone shaking out a carpet. This is not to say other things produce seismic type vibration, you know, wind, wave action, traffic, subways, footfall, fans, etc.

Gee, it seems as if you just can’t get turntable isolation low enough. Not easily anyway. Even <10Hz resonance might not be enough for optimal performance.

https://www.ortofon.com/support/support-hifi/resonance-frequency

Apart from totally over the top designs like the Continuum Caliburn and its Castellon stand, it seems as if most designers are happy to settle for just "good enough" isolation.

On the other hand if Michael Fremer’s YouTube videos comparing the Caliburn to the Technics SL1200G are anything to go by that might be enough.

https://youtu.be/qY9YYkqW8ng

https://youtu.be/QKfs5lYZuQk

Or if not, then how much of a factor was the air/sprung suspension of the Castellon stand a factor?

http://www.continuumaudiolabs.com/legacy/caliburn/castellon.php

"For an isolation system to work, the ideal support structure must be infinitely stiff, otherwise the movement of the stand will interfere with the isolation system.

To achieve the best possible result the Castellon uses a nautical turnbuckle system which exerts a significant amount of force to cross-brace the vertical legs and resist rocking motions."