Using http api to init vault does not accept base64 gpg key but CLI does - hashicorp-vault

Question

I am using the http api for initialising vault and encrypting the seal keys and root token, but I am getting
{"errors":["error decoding given PGP key: illegal base64 data at input byte 21"]}
But when I use the CLI it works.
How do I get it working for the http api??
This done using ubuntu 18.04 and gpg (GnuPG) v2.2.4, base64 v8.28, latest vault
Here is the command for command line interface that works, and returns the seal keys and root token encrypted:
./vault operator init -key-shares=2 -key-threshold=2 -address="http://127.0.0.1:8200" -format="json" -root-token-pgp-key="mo.asc" -pgp-keys="mo.asc,mo.asc"
The above was run in the same directory as the vault instance was started using
./vault server -config=vaultconfig.hcl
The vaultconfig.hcl contains
storage "inmem" {}
listener "tcp" {
address = "127.0.0.1:8200"
tls_disable = 1
}
mo.asc was obtained using the following:
gpg --gen-key
gpg --export <generated key> | base64 > mo.asc
The command for using the http api that does not work
curl --request PUT --data #payload.json http://127.0.0.1:8200/v1/sys/init
payload.json is
{
"secret_shares": 2,
"secret_threshold": 2,
"pgp_keys": [
"mo.asc",
"mo.asc"
],
"root_token_pgp_key": "mo.asc"
}
This returns:
{"errors":["error decoding given PGP key: illegal base64 data at input byte 21"]}
But if I change the payload.json to
{
"secret_shares": 2,
"secret_threshold": 2
}
it works returning
{
"keys": [
"227e3b43a76b54008249b39285ae1063db0e2bff94bad0f349f4b7fa89195fb7d7",
"2ab2f5ec67191c26735116f5a1cc9b3bab406eff7b57d9632359a0797f2cf5fd3e"
],
"keys_base64": [
"In47Q6drVACCSbOSha4QY9sOK/+UutDzSfS3+okZX7fX",
"KrL17GcZHCZzURb1ocybO6tAbv97V9ljI1mgeX8s9f0+"
],
"root_token": "s.s2GZsomY2tGJfQzHGFjqlYNu"
}
It seems the CLI command accepts that my gpg is base64 encrypted, but the http api does not accept it is encrypted. Although it seems the CLI is using the http api underneath. The http api is working, but only when I add the asc file to the payload.json it does not work.
Am I missing something?
How do I think this so I get encrypted root token and keys when initialising vault via http api?
Thanks