Invalid handling of the "jsonApiBasePath" in EntityToJsonApi

The __construct() of \Drupal\jsonapi_extras\EntityToJsonApi has the following code:

    assert(is_string($jsonapi_base_path));
    assert($jsonapi_base_path[0] === '/');
    assert(substr($jsonapi_base_path, -1) !== '/');
    $this->jsonApiBasePath = $jsonapi_base_path;

It means that $jsonapi_base_path shouldn't start from and end by a slash. However, the calculateContext() method expects that $this->jsonApiBasePath is ended by a slash.

$path = sprintf('%s%s/%s', $this->jsonApiBasePath, $resource_path, $entity->uuid());

Also, why jsonapi and jsonapi_extras have exactly same (symbol-to-symbol) EntityToJsonApi? The jsonapi.entity.to_jsonapi service uses \Drupal\jsonapi\EntityToJsonApi when jsonapi_extras disabled and \Drupal\jsonapi_extras\EntityToJsonApi oterwise. It would be logically to have a decorator (in current scenario the dublucating services just isn't needed).