This isn't entirely true……
You're basically saying that because our measurement system is arbitrary, the numbers that are yielded as a result of our measurements are irrelevant. Sure, the exact numbers assigned to said measurements might be arbitrary, however the relationship between values still exists. As proportions, percentages, whatever. However you choose to measure, things still relate to each other in some way.
My understanding of the 432Hz conspiracy doesn't rely so heavily on the number "432" vs "440", so much as it relies on the correspondence between our vibration, the earth's vibration, and the vibrations coinciding with 432Hz. Again, rearrange these numbers any way you like, but there is still a relationship between the earth, us, sound, etc.