Yea, as the whole dimensions not as planets. So when Soul King who was stabilizing the realms died the destruction started on the whole 3 realms as shown :
Here
The destruction of these whole realms were gonna affect the Garganta. We know that the WoL was affected not geologically, meaning not as a planet, but it hints us to the whole dimension of it being destroyed since human since couldn't explain it. Scan : Here
As we know the whole realms were made by Soul King. For Yhwach to achieve his plan where
nor life or death would exist he would have to undo the whole cosmology. Here we see that the world before SK created the realms had nor life or death. Soul King also Created the cycle of souls after he created the Universal sized Realms. So logically if you wanted to destroy the cycle of life and death to revert it back in the beginning you would need to destroy the whole Realms as a dimension.
Even if Yhwach didn't want to revert it back and create smth new he would need the full power of Soul King.
Scan
Soul King has the power to create and reshape the realms. This is also shown on how Hikone was going to be the fuel to these realms.
So in the end by any means Yhwach would have to destroy the Soul Society as a dimension to achieve his plan and not just the planet.