Using async with .NET Core and nHibernate

In the .NET Core I know that we have async and await to request async .

So far so good, but many frameworks on the market are creating methods with the MetodoAsync() signature and have the method without being async Metodo() .

We can use async so

[HttpGet]
public async Task<JsonResult> Get()
{
    return await Task.Run(() => Json(_fachadaGrupo.BuscarTodos()));
}

Remembering that in internal methods _fachadaGrupo.BuscarTodos() . the async method does not exist, it uses a connection to the nHibernate database, and it does not have the Async() method at the moment. So I wanted to know if this still has the same efficiency and the same logic happens internally in which thread is freed up for new requests . Or it is the same as not having.

 // facade
    public IEnumerable<GrupoDto> BuscarTodos()
    {
        return _buscarTodos.Buscar();
    }


    // Serviço
    public IEnumerable<GrupoDto> Buscar()
            {
                IRepositorioGrupo repositorioGrupo = new RepositorioGrupo(_nHibernateHelper);

                return repositorioGrupo.Lista(_usuario);
            }

// repositorio 
public IEnumerable<GrupoDto> Lista(Usuario usuario)
        {
            Usuario usuarioAlias = null;
            Grupo grupo = null;
            GrupoDto grupoDto = null;

            return Sessao.QueryOver(() => grupo).JoinAlias(() => grupo.Usuario, () => usuarioAlias)
                .SelectList(list => list.Select(() => grupo.Id).WithAlias(() => grupoDto.Id)
                .Select(() => grupo.Descricao).WithAlias(() => grupoDto.Descricao))
                .TransformUsing(Transformers.AliasToBean<GrupoDto>())
                .Where(g => g.Usuario == usuario).OrderBy(g => g.Id).Desc.List<GrupoDto>();
        }