In #1810480: Provide the plugin_id to support views metadata integration dawehner painstakingly added the plugin_id to each handler in each export. But in #1851086: Replace admin/people with a View, I tried to add a new view and didn't notice it was missing them.
We don't necessarily care that this is checked on runtime, but we should know during tests.
Eventually we could consider adding it to something like #1842956: Add hook_config_validate(), but in the meantime we could test each view as it passes through ViewTestData::importTestViews().