The “it is further decreed that” starts above the passage, and nothing indicates that the “decreed” status has changed. The language of the passage is dogmatic, not theoretical.
As to them being “completely different things”, you might think so, and I might think so, but the question is whether Pope Damasus thought so, and the passage clearly indicates that he thought that the primacy of Rome and its equal founding by Peter and Paul, which included, in his mind, their simultaneous martyrdom, were inextricably tied together. I am supported in this by the following passage by a Catholic author. Note he also believes that the sentnece about Peter and Paul dying together are essential to Damasus’s argument for the primacy:
In a decree issued in 382, Damasus categorically states that the holy Roman church has been placed at the forefront not by the concilar decisions of other churches… To prove this point, Damasus quotes Matthew 16: 18-19. Then he adduces the companionship of the Apostle Paul who, too, won the martyr’s crown along with Peter in the city of Rome under the Emperor Nero. Damasus inisists this that this happened at the same time and on the same day. By their presence and venerable triumph they set the church of Rome at the forefront over the other churches in all the cities of the world. (citing Jurgens) (my emphasis). George Kaitholil, SSP, Church: The Sacrament of Christ, pp. 97-98.