1.20.2 JSON smelting recipe output with count > 1 no longer works in 1.20.2

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In 1.19.2 and prior to that, it was possible to create a smelting recipe that produced a stack of more than one result item (e.g. 1 dirt smelts to 2 diamonds) by using the following in the recipe JSON:

"result": {
    "item": "minecraft:diamond",
    "count": 2
  },

This was added by forge, it is not vanilla behaviour (in vanilla you can only say "result": "minecraft:diamond").

After updating to 1.20.2, the above method does not work, and when parsing the JSON file it gives this error:

Not a string: {"item":"minecraft:diamond","count":2}

I assume this means it is looking for just the string "minecraft:diamond", the only behaviour allowed in vanilla, rather than JSON object that forge used to allow. Is there a new way to replicate the old behaviour in 1.20.2?