mutation productDelete Issue

Wondering why this causes “Bad Request” response:

{

“query”: “mutation {productDelete(input: {id: “gid://shopify/Product/7883881873591”}) {deletedProductId userErrors {field message} }}”

}

… but this is successful:

{
“query”: “mutation productDelete($input: ProductDeleteInput!) {productDelete(input: $input) {userErrors {field message} }}”, “variables”: { “input”: { “id”: “gid://shopify/Product/7883881873591” } }
}