Subresources routes in symfony 5 with API-platform - symfony

Question

I am trying to declare a subresource in my symfony app. I followed the api-platform doc about it: https://api-platform.com/docs/core/subresources/
The subresource does appear in the routes, but not under its parent resource.
The routes I currently have:
api_files_get_collection GET ANY ANY /api/files.{_format}
api_files_post_collection POST ANY ANY /api/files.{_format}
api_files_get_item GET ANY ANY /api/files/{id}.{_format}
api_files_patch_item PATCH ANY ANY /api/files/{id}.{_format}
api_files_put_item PUT ANY ANY /api/files/{id}.{_format}
api_external_subscription_requests_get_collection GET ANY ANY /api/external_subscription_requests.{_format}
api_external_subscription_requests_post_publication_collection POST ANY ANY /api/subscribe
api_external_subscription_requests_get_item GET ANY ANY /api/external_subscription_requests/{id}.{_format}
The routes I would like to have:
api_files_get_collection GET ANY ANY /api/files.{_format}
api_files_post_collection POST ANY ANY /api/files.{_format}
api_files_get_item GET ANY ANY /api/files/{id}.{_format}
api_files_patch_item PATCH ANY ANY /api/files/{id}.{_format}
api_files_put_item PUT ANY ANY /api/files/{id}.{_format}
api_files_external_subscription_requests_get_collection GET ANY ANY /api/files/{id}/external_subscription_requests.{_format}
api_files_external_subscription_requests_post_publication_collection POST ANY ANY /api/files/{id}/subscribe
api_files_external_subscription_requests_get_item GET ANY ANY /api/files/{id}/external_subscription_requests/{id}.{_format}
Code in App\Entity\File.php:
/**
* #ORM\Entity
* #ApiResource(
* attributes={"order"={"createdAt": "DESC"}},
* collectionOperations={
* "get"={
* "normalization_context"={"groups"={"model:timestampable", "file:collection:read"}},
* },
* "post",
* },
* itemOperations={
* "get"={
* "normalization_context"={"groups"={"model:timestampable", "file:item:read"}},
* },
* "patch",
* "put"
* },
* )
*/
class File
{
// ...
/**
* #ORM\OneToMany(targetEntity="App\Entity\ExternalSubscriptionRequest", cascade={"all"}, mappedBy="file")
* #Groups({
* "file:collection:read",
* "file:item:read"
* })
* #ApiSubresource()
*/
private $external_subscription_requests;
// ...
}
Code in App\Entity\ExternalSubscriptionRequest.php:
/**
* #ORM\Entity
* #ApiResource(
* collectionOperations={
* "get",
* "post_publication"={
* "method"="POST",
* "path"="/subscribe",
* "controller"=SubscribeToConso::class,
* }
* },
* itemOperations={
* "get",
* },
* )
*/
class ExternalSubscriptionRequest
{
// ...
/**
* #var File the file this request was made for
*
* #ORM\ManyToOne(targetEntity="App\Entity\File", inversedBy="external_subscription_requests")
* #ORM\JoinColumn(referencedColumnName="id", nullable=false)
*
* #Groups({
* "external_subscription_request:collection:read",
* "external_subscription_request:item:read"
* })
*/
public $file;
// ...
}