ocean and water_polygon layers in shortbread style duplicate zooms

[lonvia]

The ocean layer has a definition for zoom 0-13:

spirit/shortbread.yaml

Lines 13 to 16 in f002046

	- minzoom: 0
	maxzoom: 13
	extent: 2048
	file: shortbread/ocean.sql.jinja2

and one for zoom 0-14:

spirit/shortbread.yaml

Lines 17 to 19 in f002046

	- minzoom: 0
	maxzoom: 14
	file: shortbread/ocean.sql.jinja2

The water_polygons layer defines zoom 5-13

spirit/shortbread.yaml

Lines 26 to 29 in f002046

	- minzoom: 5
	maxzoom: 13
	extent: 2048
	file: shortbread/water_polygons.sql.jinja2

and zooms 4-14:

spirit/shortbread.yaml

Lines 30 to 32 in f002046

	- minzoom: 4
	maxzoom: 14
	file: shortbread/water_polygons.sql.jinja2

Is that intentional? It looks like tilekiln will just choose one at random when multiple definitions are given for a zoom level.