There is much to say about the symbolism of seals, and perhaps there is even an essential meaning to such symbols rather than one of mere association. In that sense they could truly represent their meaning in some way. But I digress.
A seal is a symbol to which a spirit has been bound. That’s it. Maybe it developed through tradition, maybe it occurred in a conscious magical act, or maybe the spirit provided it. All these questions about which are the authentic seals, or confusion over different seals existing for the same entity are themselves coming from a position of misunderstanding. The antecedent to the Ars Goetia, for instance, contains no seals for the spirits it lists. And then they suddenly appear out of nowhere. And, of course, they differ from manuscript to manuscript. If you know about the book of spirits that medieval magicians kept, then this all makes sense. You could draw any symbol you like in such a book (the best way to create them is another matter) and bind the spirit to it (or the entire ritual system for that matter, including the supposed hierarchies) for your personal workings. As such, by working a grimoire by the book, so to speak, or even in using its seals, a magician is in a sense piggybacking on the work and pacts of the magician who authored the grimoire. I think, ultimately, you’d want to throw even this away as another crutch. Get your own set of seals for your own heirarchy of spirits. Who is at the head of the demonic legions? Whoever is commanding them. Build your own infernal empire.