Trouble Faceting on Text Field Terms in Facet Queries

I'm trying to use faceting to look at the terms that were indexed into a field, realizing this is a bit atypical, but I'm using it as a debugging tool. The problem is I'm not seeing any faceted terms.

I think this is something to do with later version of Solr, perhaps v8 or v9, but not finding any reference to that. I do have a shell script that reproduces the problem pretty easily:

#!/bin/bash

COLLECTION=test
NUM_SHARDS=1  # Solr v9 (maybe earlier) doesn't restrict to single shard, BUT doesn't matter for our small dataset
TERMS=test
TYPE=text_general
SUFFIX=_t
FIELD=test$SUFFIX
DOC_ID=doc1

echo;echo
echo Removing Any Previous collection - will give error if run for the first time
curl "http://localhost:8983/solr/admin/collections?action=DELETE&name=$COLLECTION"

echo;echo
echo Creating Collection $COLLECTION with $NUM_SHARDS shards
curl "http://localhost:8983/solr/admin/collections?action=CREATE&name=$COLLECTION&numShards=$NUM_SHARDS&replicationFactor=1&maxShardsPerNode=$NUM_SHARDS"

echo;echo
echo Adding doc id = $DOC_ID with TERMS = $TERMS
curl -X POST "http://localhost:8983/solr/$COLLECTION/update?commit=true" \
 -H "Content-Type: application/json" \
 -d "[
   {
     \"id\": \"$DOC_ID\",
     \"$FIELD\": \"this is a test of the Solr indexing system: TERMS = $TERMS\"
   }
 ]"

echo;echo
echo Query for all docs
curl "http://localhost:8983/solr/$COLLECTION/select?q=*:*"

echo;echo
echo Query for TERMS = $TERMS
curl "http://localhost:8983/solr/$COLLECTION/select?defType=edismax&qf=$FIELD&q=$TERMS&rows=1"

echo;echo
echo Testing Old Facet API
curl "http://localhost:8983/solr/$COLLECTION/select?q=*:*&rows=0&facet=true&facet.field=$FIELD"

echo;echo
echo Testing New Facet API
curl "http://localhost:8983/solr/$COLLECTION/select?q=*:*&rows=0&json.facet=%7Bwords:%7Btype:terms,field:content_t,limit:10%7D%7D"

echo;echo
echo Done

If I put an echo in front of my curl command that inserts the document you can see that the variable substitution looks correct:

curl -X POST http://localhost:8983/solr/my-files/update?commit=true -H Content-Type: application/json -d [
   {
     "id": "doc1",
     "test_t": "this is a test of the Solr indexing system: TERMS = test"
   }
 ]

Then doing a null query you can see that the document is ndexed:

Query for all docs
{
  "responseHeader":{
  "zkConnected":true,
  "status":0,
  "QTime":0,
  "params":{
    "q":"*:*"
  }
},
"response":{
    "numFound":1,
    "start":0,
    "numFoundExact":true,
    "docs":[ ]
  }
}

Searching for the terms seems to work:

{
  "responseHeader":{
    "zkConnected":true,
    "status":0,
    "QTime":0,
    "params":{
      "q":"test",
      "defType":"edismax",
      "qf":"test_t",
      "rows":"1"
    }
},
"response":{
  "numFound":1,
  "start":0,
  "numFoundExact":true,
  "docs":[{
    "id":"doc1",
    "test_t":"this is a test of the Solr indexing system: TERMS = test",
    "_version_":1847191228405252096,
    "_root_":"doc1"
  }]
}

But notice what happens when I try to facet:

echo;echo
echo Testing Old Facet API
curl "http://localhost:8983/solr/$COLLECTION/select?q=*:*&rows=0&facet=true&facet.field=$FIELD"

Gives the output:

Testing Old Facet API
{
  "responseHeader":{
  "zkConnected":true,
  "status":0,
  "QTime":0,
  "params":{
    "q":"*:*",
    "facet.field":"test_t",
    "rows":"0",
    "facet":"true"
  }
},
"response":{
  "numFound":1,
  "start":0,
  "numFoundExact":true,
  "docs":[ ]
},
"facet_counts":{
  "facet_queries":{ },
  "facet_fields":{
    "test_t":[ ]
  },
  "facet_ranges":{ },
  "facet_intervals":{ },
  "facet_heatmaps":{ }
}
}

Similar results if I try the newer JSON syntax:

echo;echo
echo Testing New Facet API
curl "http://localhost:8983/solr/$COLLECTION/select?q=*:*&rows=0&json.facet=%7Bwords:%7Btype:terms,field:content_t,limit:10%7D%7D"