Explicit joins (on backlinks?) are slow (possible 6.x regression)

[elprans]

Given this schema:

type Bar;
type Foo {
  required bar: Bar;
};

The following query appears to be triggering a seqscan on Bar

select (select Foo filter .id = <uuid>"some-id") {
  comp := (
    with sourceId := .id
    select Bar
    filter .<bar[is Foo].id = sourceId
  )
};

  │     Time           Cost  Loops  Rows  Width │ Plan Info
┬ │   1586.4     8461728.11    1.0   1.0     32 │ ➊ IndexOnlyScan relation_name=Foo, scan_direction=Forward,
│ │                                             │ index_name=constraint 'std::exclusive' of property 'id' of object type 'default::Foo'
╰ │   1586.4     8461723.66    1.0   1.0     32 │ ➋ Aggregate strategy=Plain, partial_mode=Simple
  │   1586.4     8460473.64    1.0   1.0     16 │ SeqScan relation_name=Bar

For some additional context, this is a simplified version of a query that the UI data inspector runs when working on required links with access policies (to side-step the "required link 'bar' is hidden by access policy" error).