Nothing quite so explicit as that I think, though obviously preserving something is always the intent when carving shit into stone.
Ptolemaic Egypt was a culture populated by Greek and Egyptian speakers. Of those who were literate, many would only be able to read Demotic or Greek, but meanwhile there is a 2500 year history (at THAT time. Egypt is ridiculously old) of Hieroglyphics being the “official” way to write things down, and the scribal and priestly classes would be part of the cultural elites. Combine that with the Ptolemies attempting to situate themselves as both continuing Alexander’s legacy and being fully Egyptian, and there will be a place for all three scripts. Engraving laws onto stones and placing them in prominent public spaces would have been a pretty common way to “publish” them in a way that’s meant to be durable and secure. See the Code of Hammurabi and Draco’s code for just a couple of examples.
The fact that Alexandria was cosmopolitan and had a sophisticated regime ruled by elites who were foreign but invested in the local traditions created a situation where this was done often enough for some to survive, several in fact, although the Rosetta Stone was the first found/identified.
Seems like it was pretty analogous, though it seems like there was a ritual value to hieroglyphics and the older forms of the language that’s a few steps beyond even what ecclesiastical Latin is today. I would say there would be a certain sense that something could only have top-tier religious import if it was set down in Medut Netjeru (“the Words of the Gods”). I thought this article by an Egyptologist was pretty interesting.