Survey Creator: JSON Editor incorrectly flags a valid property value as invalid

[JaneSjs]

T26135 - Custom Descriptive Demo causes error in the textSize property
https://surveyjs.answerdesk.io/internal/ticket/details/T26135

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In this demo, a custom "textSize" property is declared as follows:
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{
   name: "textSize",
   category: "general",
   visibleIndex: 3,
   default: "medium",
   choices: [
      { value: "small", text: "Small" },
      { value: "medium", text: "Medium" },
      { value: "large", text: "Large" }
   ]
}

In a survey JSON, this property is stored as follows:

However, a JSON Editor displays the following error:

"Line: 7. The property value: 'large' is incorrect for property 'textSize'."

If you fix this error, a property is updated as follows:

"textSize": "{\"value\":\"small\",\"text\":\"Small\"}"

However, this value is also considered invalid:

Line: 7. The property value: '{"value":"small","text":"Small"}' is incorrect for property 'textSize'.