>  I always understood it to be best practice to use these boundary ways to form the areas. 

It's certainly not how the overwhelming majority of editors do things. Simply because it doesn't really offer any benefits and only complicates things. Multipolygons should only really be used when they are necessary (e.g. when there's a hole in the area).

> For folks using iD and JOSM, having a bunch of relations in the editing area can make things quite frustrating to edit.

Normal editing operations such as changing tags or moving the outline around a bit work more or less fine and you won't even necessarily notice that you're editing a multipolygon. Even iD has that rudimentary level of support. Anything that involves creating new areas or deleting (parts) of areas is going to be more of a hassle than it needs to be though.
More problems start to pile up when you want to do things that are a bit more advanced, such as joining or splitting areas, etc... Editor support for operations on multipolygons simply is not as good as it is for simple closed ways. E.g. splitting multipolygon areas wasn't supported in josm and had to be done manually until I implemented it recently while it has been available for normal closed way areas for ages. These problems might not be as noticeable for users of editors that don't have these features in the first place and where doing things manually is the only way anyway, but it's a big annoyance and slowdown for users of advanced editors.

> Having multiple ways sharing the same nodes certainly makes it very difficult to select the way you actually want to edit much of the time.

> JOSM has the rather cumbersome "middle click to cycle through coincident objects".

You can select areas as normal by double clicking in them (josm), so selecting different closed way areas even when the ways are partially overlapping is a non-issue and you won't even notice it. If there are multiple linear ways overlapping, you can select them by cycling through them by holding the alt modifier key while clicking or selecting them from the popup list that appears when middle clicking on them.

> JOSM pulling all relation selection/editing into it's own side interface. And don't get me started on relations of relations ha.

Editing multipolygons works just like for any other objects. You _can_ select and edit them using the relation editor if you want to, but that is rarely necessary. Using the dedicated relation editor interface for other relations is a good thing since the properties of relations are so different to other objects and the normal editing interface is not intended for that (e.g. you need to be able to edit the member objects somehow).
Relations of relations are not relevant for multipolygons or areas that are the topic here.


Anyway. The multitude of issues with overlapping or not quite joining ways here in this area seem to have been here since they were created by a user who apparently didn't care too much and were not created by subsequent edits. This is not something that is an inherent fault of simple closed way areas.

https://www.openstreetmap.org/changeset/108889099



