How do I count unique values within variant arrays?

In this example we want to know how many sofas in our collection have a 1.5 seater option available.

If the records in our collection looked like this:

{
  "id": "6890532208798",
  "name": "blue sofa",
  "variant_sizes": [
    "3-Seater (Queen)",
    "2.5-Seater (Double)",
    "1.5-Seater (Single)",
  ]
},
{
  "id": "3892532108799",
  "name": "red sofa",
  "variant_sizes": [
    "2.5-Seater (Double)",
    "1.5-Seater (Single)",
  ]
},
{
  "id": "88925325668797",
  "name": "green sofa",
  "variant_sizes": [
    "3-Seater (Queen)",
    "2.5-Seater (Double)",
  ]
},

CODE

Then running a query with a filter like the example below would return the records for the blue and red sofa which both have 1.5 seater options i.e. 2 sofas come in this size option.

Example of query:

{
  "q": "",
  "filter": "variant_sizes ~ ['1.5-Seater (Single)']"
}

CODE

An alternative option is to run a query with a count on variant_sizes like the example below. The response would return all 3 records regardless of their seating options, but the count within the response would also identify that 2 sofas have 1.5-Seater (Single) options.

Example of query:

{
  "q": "",
  "count": "variant_sizes"
}

CODE

Example of response:

"variant_sizes":{
  "count": {
              "3-Seater (Queen)": 2,
              "2.5-Seater (Double)": 3,
              "1.5-Seater (Single)": 2
  }
}

CODE

In the example below the elements within "variant_sizes" represent the in-stock size options so there are repeated entries i.e. the blue sofa has three 1.5-Seater options in stock

{
  "id": "6890532208798",
  "name": "blue sofa",
  "variant_sizes": [
    "3-Seater (Queen)",
    "2.5-Seater (Double)",
    "1.5-Seater (Single)",
    "1.5-Seater (Single)",
    "1.5-Seater (Single)",
  ]
},
{
  "id": "3892532108799",
  "name": "red sofa",
  "variant_sizes": [
    "2.5-Seater (Double)",
    "2.5-Seater (Double)",
    "1.5-Seater (Single)",
  ]
},
{
  "id": "88925325668797",
  "name": "green sofa",
  "variant_sizes": [
    "3-Seater (Queen)",
    "2.5-Seater (Double)",
    "2.5-Seater (Double)",
  ]
},

CODE

Running a query with the same filter we ran before will still return the records for the blue and red sofa i.e. 2 records, however running a query with the same count as we did before will now return "1.5-Seater (Single)": 4 which tells us the stock availability of the 1.5-Seater not how many sofas have 1.5 seater options