The article I wrote indicates the printer rez ratio is relevant for glossy type papers. I didn't test watercolor or canvas since I don't really print on that stuff. The odds are that exceeding 360 and using Finest Detail won't benefit from 720 PPI output with Finest Detail on because the papers/canvas can't hold the detail.
I have tested it and, a bit to my own surprise, there can be a significant amount
of additional resolution above 300 or 360 PPI even when printing on non-glossy paper. On my Canon printer I can resolve 600 PPI detail of medium and high contrast on e.g. Hahnemühle Matt FineArt PhotoRag Bright White paper, so I have to assume it's also possible to achieve 720 PPI on Epsons.
Having said that, and while it is there, the resolution is not as well defined as on glossy paper because of the surface structure of matt paper and potentially more ink diffusion. That diffusion will also render fine detail darker, which may also lead to differences due to the orientation of the detail. On my printer the lines parallel to the print head travel direction are thinner and show less diffusion, compared to lines in the paper feed direction which are darker and slightly 'thicker'.
So in the end, the additional resolution above 300/360 PPI can significantly increase the effective output resolution on some matt (maybe not on the coarsest canvas) paper as well.