It refers to the style of things built under Badr al-Jamali who was bought as an Armenian slave, converted to Islam, made it to a Vezir and would hire Armenian craftsmen and architects to renovate some towns in Syria and Egypt.

When a guide tells you that the city walls in Cairo are from the Armenian period he means they were built by people taught by Armenian architects and are similar to the walls of Edessa. If a Mosque looks somewhat like a Byzantine church this might also be either a really old building or a remnant of the Armenian period.

Source: Մսըրլյան, Գևորգ. Ականաւոր հայեր Եգիպտոսի մէջ. Cairo, 1947.