While I totally agree that historically there was an understanding of sunrise happening at different times in different places there is at least one example in RAW that suggests it is not wholly true in-setting.
The Fenicil ritual that cursed house Deidne was timed to complete just after dawn so as to catch as many Deidnes as possible without their Parmas.
The Ritual was presumably cast at Magvillus. If the variation of sunrise and sunset was radically different from place to place there would be very few if any Deidne experiencing sunrise at the same time as the Domus Magnus of house Guernicus in the on a mountain in Italy.