Menu items created (as disabled) when set to 'never'

One of my content types (page) uses node hierarchy, while none of my other types have it enabled. However, one of my content types (event) is creating menu items, even though Node Hierarchy is not active on that type (it's set to 'never' and has no parent/child types chosen in the admin/content/types edit screen).

The menu items it's creating are all set to 'disabled' so they're not visible on the site, but it's really making a mess of the menu admin screen (and I'm guessing causing other unseen issues). Screenshot of the menu items attached.

Anyone else experiencing this? I originally saw this on the 1.x version, but it has continued (I think) in the 2.x branch as well.