Processing of missed indices

I would like to clarify next situation.

Imagine, that we have thermal powers for 3 reactors, and two detectors. I would like multiple thermal power of each reactor by distance between reactor and detector. However, I include just two pairs of distances reactor-detector.

Check the code below:

from itertools import product
from dag_modelling.plot.graphviz import savegraph

from dag_modelling.core import Graph, NodeStorage
from dag_modelling.bundles.load_parameters import load_parameters
from dag_modelling.lib.arithmetic import Product

storage = NodeStorage()
index = {
    "reactor": ["A", "B", "C"],
    "detector": ["x", "y"],
}
combinations = list(product(index["reactor"], index["detector"]))
with (
    Graph(close_on_exit=True, strict=True) as graph,
    storage,
):
    load_parameters(
        format="value",
        state="fixed",
        parameters={
            "thermal_power": {
                "A": 2,
                "B": 4,
                "C": 8,
            },
            "baseline": {
                "x": {
                    "A": 0.1,
                    "B": 0.2,
                    "C": 0.3,
                },
                "y": {
                    "A": 0.01,
                    "B": 0.02,
                }
            }
        },
        labels={
            "thermal_power": {
                "A": "reactor A",
                "B": "reactor B",
                "C": "reactor C",
            },
            "baseline": {
                "x": {
                    "A": "baseline A-x",
                    "B": "baseline B-x",
                    "C": "baseline C-x",
                },
                "y": {
                    "A": "baseline A-y",
                    "B": "baseline B-y",
                }
            }
        }
    )
    parameters = storage["parameters.all"]
    Product.replicate(
        parameters["thermal_power"],
        parameters["baseline"],
        replicate_outputs=combinations,
        allow_skip_inputs=True,
        skippable_inputs_should_contain=[("C", "y")],
        name="check",
    )

for out in storage["outputs.check"].walkvalues():
    out.data

print(list(storage["outputs.check"].walkjoinedkeys()))

savegraph(graph, "graph.dot", show="all")

In check-output I will see 6 items, but I 5 items are expected.

Is it bug or feature?

cc @maxfl @tsegelnik