I referred this article and as per this https://kb.vmware.com/selfservice/microsites/search.do?language=en_US&cmd=displayKC&externalId=21211... for configuring Oracle RAC on VSAN, vm disk should be thick eager zeroed how this can be thick in vsan as in vsan only thin format we have for the disks.
You have to use 'Object space reservation %' to 100% in VSAN Storage Policy for the VM. This will provision VM as Thick.
You can either use PowerCLI or the ESXi command line to create thick eager zeroed disks. Both methods are detailed within the KB that you linked. I'm unsure if using the old fat client and choosing thick eager zeroed works or not - I've been meaning to test that method as well but have not had a chance.