Zoom level partially not used for validity range

[Bibi56]

I've 2 vector mbtiles. 1.mbtiles valid for zoom level 1 and 5.mbtiles for zoom level 5.

This issue is correlated with mojodna/tl#21, but different.

Starting:
tessera 'merge:?source=mbtiles://./1.mbtiles&source=mbtiles://./5.mbtiles'

I get: 1.mbtiles rendered at zoom level 1 (fine), from 2 to 4 (overzoom, acceptable), zoom level clipped between 1 and 5 (fine) but at level 5 I see the 1.mbtiles and the 5.mbtiles rendered, the first one being overzoomed.
As the zoom level of tessera prevents overzooming (the slippy map goes to zoom level 5 only), tile-merge should be able to enable/disable overzooming at intermediate level.
I can change the style in order to skip the display of the 1.mbtiles at zoom level 5 but I wonder if that's not something tilelive-merge should manage.

Another vision is to consider that some layers should be aggregated (here same date, just simplified at low zoom level) or blended (for instance mbtiles representing streets and buildings).

The info given by tl is conform to my expectation, not the rendering by tile-merge.

tl info 'merge:?source=mbtiles://./1.mbtiles&source=mbtiles://./5.mbtiles'| jq .

{
  "id": "1z,5z",
  "bounds": [
    -180,
    -85.0511,
    180,
    83.66590018583321
  ],
  "center": [
    0,
    -0.7034423338343103,
    0
  ],
  "format": "pbf",
  "maxzoom": 5,
  "minzoom": 1,
  "name": " + ",
  "scheme": "tms",
  "vector_layers": [
    {
      "id": "land_polygons_z1",
      "description": "",
      "minzoom": 1,
      "maxzoom": 1,
      "fields": {
        "FID": "Number"
      }
    },
    {
      "id": "land_polygons_z5",
      "description": "",
      "minzoom": 5,
      "maxzoom": 5,
      "fields": {
        "FID": "Number"
      }
    }
  ]
}

[Bibi56]

Using the protocol blend (tilelive-blend), it does what I'm looking for (except that it doesn't recognize the minzoom and maxzoom in order to restrict the range to valid zoom levels).