why would "{!parent}" return a child document?

[Dmitri Maziuk]

Hi all,

we're still struggling here with child documents, here's my problem du 
jour (solr 8.11):

in the index:
```
{
  "id": "W0178E6",
  "odams.identifier": "W0178E6",
  "is_child": false,
...
  "child_objects": [
  {
    "id": "W0178E6!W0178F2",
    "odams.identifier": "W0178F2",
    "is_child":true
  },
...
```
with more children:

"id": "W0178E6!W0178EX",
"id": "W0178E6!W0178F9",
"id": "W0178E6!W0178F7",
"id": "W0178E6!W0178F3",
"id": "W0178E6!W0178F1",
"id": "W0178E6!W0178EZ",
"id": "W0178E6!W0178EY",
"id": "W0178E6!W0178EO",
"id": "W0178E6!W0178EM",

My reading of The Fine Manual @ 
https://solr.apache.org/guide/8_11/searching-nested-documents.html is that
 `q={!parent which="*:* +is_child:false}(+odams.identifier:W0178F2)`
should return the parent: W0178E6.

What I get instead is
```
{
  "responseHeader":{
    "status":0,
    "QTime":18,
    "params":{
      "q":"{!parent which=\"*:*  is_child:false\"}( 
odams.identifier:W0178F2)",
      "debugQuery":"true"}},
  "response":{"numFound":1,"start":0,"numFoundExact":true,"docs":[
      {
...
        "id":"W0178E6!W0178EX",
        "odams.identifier":"W0178EX",
...
    }]
 },
  "debug":{
    "rawquerystring":"{!parent which=\"*:*  is_child:false\"}( 
odams.identifier:W0178F2)",
    "querystring":"{!parent which=\"*:*  is_child:false\"}( 
odams.identifier:W0178F2)",
    "parsedquery":"AllParentsAware(ToParentBlockJoinQuery 
(+odams.identifier:W0178F2))",
    "parsedquery_toString":"ToParentBlockJoinQuery 
(+odams.identifier:W0178F2)",
    "explain":{
      "W0178E6!W0178EX":"\n0.0 = Not a match\n"},
    "QParser":"BlockJoinParentQParser",
    "timing":{
...
```

Any ideas why?
What does is even mean `"W0178E6!W0178EX":" 0.0 = Not a match"` with the 
"W0178E6!W0178EX" document returned?

Any hints welcome, TIA
Dima