I would quantify my support as half-hearted at best. I fully understand your point and see its logic but I would not want it to be the default. My rationale is simple, when I go into the Members Pages I want to see those observations that are new and not have to search for them. Displaying in date submitted order gives me this. You are right of course, in a lot of cases this will be the same as date of observation but some members are posting old observations, some from several years ago and depending on their posting mix these could be well down the list with your suggested scheme and thus difficult to find.
Ideally it would useful to have a choice of sort order so everybody could have what they want and maybe the default held against each members individual profile. However I suspect this is a step too far and likely beyond the capabilities of the tool used to create the site.