Can bind question outside ngSwitch; Cannot bind inside ngSwitch Angular 10 code example

Example 1: *ngSwitch

<container-element [ngSwitch]="switch_expression">
  <!-- the same view can be shown in more than one case -->
  <some-element *ngSwitchCase="match_expression_1">...</some-element>
  <some-element *ngSwitchCase="match_expression_2">...</some-element>
  <some-other-element *ngSwitchCase="match_expression_3">...</some-other-element>
  <!--default case when there are no matches -->
  <some-element *ngSwitchDefault>...</some-element>
</container-element>

Example 2: angular switch component

<container-element [ngSwitch]="switch_expression">
  <some-element *ngSwitchCase="match_expression_1">...</some-element>
</container-element>