Also, it is next to impossible to dismiss the case of visiting the graves as anything but a case of genuine abrogation.
IMHO, the case you cite is particularly easy to resolve. The early Muslims had practiced many pagan rituals and customs before Islam. What they used to do at grave sites was contrary to Islam. Old habits are hard to break. Enough time needed to be allowed before Muslims fully grasped the concept of Tawheed (monotheism) and abandon customs that contradict it. That was
the contingency for the prohibition made by the Prophet (PBUH) of visiting graves, though he did not say that. Many scholars made that explanation. Perhaps that's what you meant by the dynamic phase of Islam?
When enough time had passed, and the Prophet (PBUH) no longer feared that Muslims would engage in pagan customs, he allowed visiting the graves, because, as he said, they remind of death. That too was the contingency for the new directive!
I therefore do not actually see this as a case of abrogation per se. Both rulings are contingent IMHO. So, both rulings remain valid, if their contingencies arise.
That said, the narration on which this case is based, clearly says that it was the Prophet (PBUH) who issued both directives. Thus, both directives may have been the Prophet's opinion (PBUH) and not an inspiration. In fact, several versions of the narration, told by Burayda, Abu-Hurayra and others, and reported by Muslim, say that the allowance came after the Prophet (PBUH) asked God to let him visit his mother's grave and God allowed him. That may be interpreted as God abrogating a personal decision of the Prophet (PBUH).