In using the playground I find that
tags get rendered literally into Excalidraw text in the rendered drawing. You can see the tags in the JSON that is being output as well.

"D1": {
"id": "D1",
"labelType": "text",
"text": "Meets Target
Criteria?",
"type": "diamond",
"x": 432.84765625,
"y": 611.21875,
"width": 230.46875,
"height": 230.46875,
"containerStyle": {
"fill": "#ff9999",
"stroke": "#cc0000",
"stroke-width": "3px"
},
"labelStyle": {}
},