The Allies wield both carrot and stick, compelling Romania to comply, naturally contradicting Ferdinand I's wish to remain "neutral" until the end, so it's understandable that Ferdinand I felt some dissatisfaction.
Of course, Ferdinand I had many small schemes. His agreement to join the Allies certainly wasn't solely due to their threats; fundamentally, it also indicated he had a relatively optimistic view about the Allies' prospects.
Although the entry of the United States has greatly boosted the momentum of the Allies, the Allies currently hold a military advantage in Europe, not to mention the German Country's East Africa hasn't entered the fray overseas.
Crown Prince Rudolph doesn't care about Ferdinand I's little schemes; he only needs Romania to obediently follow the arrangement of the Allies, or rather, that of Germany and Austria-Hungary.
