Well no it didn't. It identified them by former offices. "Late delegate", not "Delegate", "late Minister" not "Minister", etc. All three men represented the United States alone and not any individual state.
It's stated in the Texas Constitution we have an *inalienable* right to do so. Whether it's legal or not means very little at that point.
Treaty of Alliance with France, 1778
In faith where of the respective Plenipotentiaries, to wit on the part of the most Christian King Conrad Alexander Gerard royal syndic of the City of Strasbourgh & Secretary of his majestys Council of State and on the part of the United States Benjamin Franklin Deputy to the General Congress from the State of Pensylvania and President of the Convention of the same state, Silas Deane heretofore Deputy from the State of Connecticut & Arthur Lee Councellor at Law have signed the above Articles both in the French and English Languages declaring Nevertheless that the present Treaty was originally composed and concluded in the French Language, and they have hereunto affixed their Seals
Treaty of Commerce with France, 1778
The most Christian King, and the thirteen United States of North America, to wit, New Hampshire, Massachusetts Bay Rhode island, Connecticut, New York, New Jersey, Pennsylvania Delaware, Maryland, Virginia North-Carolina, South Carolina & Georgia, willing to fix in an equitable and permanent manner the Rules which ought to be followed relative to the Correspondence & Commerce which the two Parties desire to establish between their respective Countries, States, and Subjects, hi most Christian Majesty and the, said United States have judged that the said End could not b, better obtained than by taking for the Basis of their Agreement the most perfect Equality and Reciprocity, and by carefully avoiding all those burthensome Preferences, which are usually Sources of Debate, Embarrasment and Discontent; by leaving also each Party at Liberty to make, respecting Commerce and Navigation, those interior Regulations which it shall find most convenient to itself; and by founding the Advantage of Commerce solely upon reciprocal Utility, and the just Rules of free Intercourse; reserving withal to each Party the Liberty of admitting at its pleasure other Nations to a Participation of the same Advantages. It is in the Spirit of this Intention, and to fulfil these Views, that his said Majesty having named and appointed for his Plenipotentiary Conrad Alexander Gerard, Royal Sindic of the City of Strasbourg, Secretary of his Majesty's Council of State, and the United States on their Part, having fully impower'd Benjamin Franklin Deputy from the State of Pennsylvania to the general Congress, and President of the Convention of said State, Silas Deane late Deputy from the State of Connecticut to the said Congress, and Arthur Lee Councellor at Law
Treaty of Commerce with Prussia, 1786:
With this view his majesty the king of Prussia has nominated and constituted as his plenipotentiary, the baron Frederick William de Thulemeier, his privy counsellor of embassy, and envoy extraordinary, with their high mightinesses the states general of the United Netherlands, and the United States, have on their part, given full powers to John Adams, esquire, late one of their ministers ple- nipotentiary for negociating a peace, heretofore a delegate in Congress from the state of Massachusetts, and chief justice of the same, and now minister plenipotentiary of the United States with his Britannic majesty; doctor Benjamin Franklin, the minister plenipotentiary at the court of Versailles, and another of their ministers plenipotentiary for negociating a peace; and Thomas Jefferson, heretofore a delegate in Congress, from the state of Virginia, and governor of the said state, and now minister plenipotentiary of the United States at the court of his most christian majesty, which respective plenipotentiaries, after having exchanged their full powers, and on mature deliberation, have concluded, settled and signed the following articles.
To suggest otherwise is simply playing semantics.