Routes listed as GET no matter what

[gekkedev]

If I generate a very default ASP/.NET Core - based CRUD controller (4 methods) with the route
[Route("[controller]/[action]")], all listed routes have the same request type (GET).
This is not how the routes are actually behaving. They're accessible by their respectively specified attributes. For example, my deletion method does only react to DELETE requests when specifying the attribute [HttpDelete]. Additionally I am using ASP's [Authorize] attribute on pretty much every controller, but gitting rid of it is not an option. Removing my custom written action filters do not seem to have any negative effect either.
Am I maybe just specifying my MVC routing template wrong? It's just copied from the given example.

Unfortunately I cannot present that much source code as it is corporate property. Might work on some further reproduction examples if it is not imagineable at all how the routes are all shown as the same request type.
Version used: 0.5.3