The photo-based system would no doubt work great if the town had only a dozen people (all of whom know each other by sight), and probably work acceptably well for up to a few dozen. It's going to suck for a town with a thousand people, though, and be utterly unusable for a city of a hundred thousand.
Textual information reaches its upper bound far before visual information.
Think reading a recipe from a cookbook vs following along with a well done YouTube recipe.
The density of information delivered via video (visually) in addition to the word messaging (via audio) is roughly 10-100X that of an all text recipe.
...and with zero added effort from the human receiving the information, because our brain natively does the visual processing.
Sure, it’s faster to follow a recipe if you’ve spent ten years learning everything about cooking and food science.
Just as it’s easier to just code something if you’ve spent years learning how to code!
The point is to lower the barrier of entry, and deliver people a higher density of information faster and easier.
For example, you can't write most useful programs without knowing what a pointer/reference is. Doesn't matter if you use visual programming or textual code.
I think you need to show your work on that calculation - because I'm worried it's going to be one of those 'a video has so many bytes of information per frame etc. etc.' claims at which point I would have to wonder why I care what color Julia Child's blouse is when preparing an omelet.
Is there an upper bound to the benefits of visual information in comparison to textual information when handling complex tasks so that when a task reaches a certain level of complexity it becomes easier to represent it in text as opposed to visually? The history of human communication would strongly suggest that there is.