Thank you for the helpful article - I was not able to find this info when searching for it.
So it seems that:
- It is not possible to upgrade VM hardware of VCSA.
- VMware does not recommend upgrading VM hardware unless you need the features.
VMware do not suggest to upgrade the VM HW and VMware tools on the appliance as it may break the VC.
I agree with not updating the VM hardware for the vCSA.