To quote Harry Turtledoves’s lizards; “Truth!”
We can theorize all we want to, but we will not know for sure what is going on until humans or machines take a closer look. We just don’t have enough data.
Here is a question about liquid CO2. Does it meander?
Water likes to meander and most channels on Mars show some signs of this. I have even seen braded channels on Mars that are very characteristic of water flows on shallow slopes.