questions about local-expand and local-apply-transformer

I found in racket 'expression is always used as the context argument of local-apply-tranformer, but, if I understand correctly, 'expression and 'top-level are excluded from generating use-site scopes for local-expand in racket 7
(from https://github.com/racket/racket/blob/41fd4f3a5e0c6d4ca0ef822b168bf33a5c9068a6/racket/src/expander/expand/definition-context.rkt#L245-L250 ).
This program(derived from #2069 ):

#lang racket

(module a racket
  (require (for-syntax racket/syntax))
  (provide use-expander)
  (define-syntax (use-expander stx)
    (syntax-case stx ()
      [(_ id arg)
       (let* ([intdef-ctx (syntax-local-make-definition-context #f #f)]
              [transformer-id (internal-definition-context-introduce
                               intdef-ctx
                               (generate-temporary 'a))])
         (syntax-local-bind-syntaxes
          (list transformer-id)
          #`(quote #,(syntax-local-value #'id))
          intdef-ctx)
         (local-expand #`(#,transformer-id arg) 'expression '() (list intdef-ctx)))])))

(require 'a)

(define x 1)

(define-syntax (expander1 stx)
  (syntax-case stx ()
    [(_ an-x)
     (begin
       (displayln (hash-ref (syntax-debug-info #'an-x) 'context))
       #'(let ([an-x 3])
           x))]))

(use-expander expander1 x)

produce

(#(60778 module) #(60785 module anonymous-module) #(61088 macro))
3

but in 6.12, there will be a use-site scope

(#(110355 module) #(110356 module anonymous-module 0) #(111968 macro) #(111969 use-site))
1

I'm not clear why the behavior is changed in the new expander. Is it intended?
If so, how to use local-apply-transformer or local-expand with internal-definition-context properly? Is generate-expand-context sufficient?

Start with the referenced definition-context.rkt section around lines 245–250 and the local-expand and local-apply-transformer entry points. Reproduce the supplied program on Racket 7 and 6.12, then inspect how internal-definition-context and generate-expand-context affect use-site scopes. Done means explaining whether the changed scope behavior is intentional and documenting the proper API usage.