See this test page, despite MediaWiki.org having its own Data namespace, it doesn't seem possible to query it.

I suspect

"JsonConfigInterwikiPrefix": {
			"value": "commons"
		}

in extension.json is to blame.

Expected behavior: just like the File namespace, local and shared namespaces playing nice and working together
What happen instead: Lua error in Module:Tabular_data at line 65: attempt to index local 'data' (a boolean value).