The short answer is "No." In different forms, this has come up before at least a few times on the forum.
A quick search in a search engine shows that Vault does require policies sent over its API to use JSON:

But Vault's JSON schema for Vault Policies doesn't seem to match that for the rest of the HashiCorp tools, I guess.
The entire policy needs to go in one value, under the "policy": key.
Tools like
hcl2json will NOT work for Vault policies:

But here's an example of a format that will work:
{
"policy": "path \"auth/*\" { capabilities = [\"create\", \"read\", \"update\", \"delete\", \"list\", \"sudo\"]"
}
The Vault API for Policies expects a .hcl policy JSON-serialized as a single string.
Please refer to the post I made about this earlier:
And a Vault Policy .hcl file to Vault-compatible .json converter I made: