This is interesting. Surely this is true for the subdiaconate, but can a man really be ordained a priest without first being ordained a deacon? Could a man be consecrated a bishop without first being ordained a priest? I'm not so sure.
Yes, a priest can be ordained to the priesthood without first being ordained to the diaconate. That's certain.
It's debated (and considered doubtful) whether a man could be ordained a bishop without first being ordained a priest. Certainly this cannot happen the way the Latin/Roman Rite is written: "Comple in Sacerdote Tuo ..." where the essential form refers to perfecting or completing "in your priest" the summit of the ministry. This applied to a non-priest would be invalid. Now, I haven't looked at the Eastern Rites, but IMO if the Rite's essential form did not specify a priest, it's possible and even likely that the consecration would be valid. There's also some speculation that a priest could ordain another man to the priesthood.