Index: src/wp-content/themes/twentytwentyone/assets/css/ie-editor.css
===================================================================
--- src/wp-content/themes/twentytwentyone/assets/css/ie-editor.css	(revision 52145)
+++ src/wp-content/themes/twentytwentyone/assets/css/ie-editor.css	(working copy)
@@ -1459,7 +1459,7 @@
 
 /* Center image block by default in the editor */
 .wp-block-image,
-.wp-block-image > div {
+.wp-block-image > div:not(.components-placeholder) {
 	text-align: center;
 }
 
Index: src/wp-content/themes/twentytwentyone/assets/css/style-editor.css
===================================================================
--- src/wp-content/themes/twentytwentyone/assets/css/style-editor.css	(revision 52145)
+++ src/wp-content/themes/twentytwentyone/assets/css/style-editor.css	(working copy)
@@ -1128,7 +1128,7 @@
 
 /* Center image block by default in the editor */
 .wp-block-image,
-.wp-block-image > div {
+.wp-block-image > div:not(.components-placeholder) {
 	text-align: center;
 }
 
Index: src/wp-content/themes/twentytwentyone/assets/sass/05-blocks/image/_editor.scss
===================================================================
--- src/wp-content/themes/twentytwentyone/assets/sass/05-blocks/image/_editor.scss	(revision 52145)
+++ src/wp-content/themes/twentytwentyone/assets/sass/05-blocks/image/_editor.scss	(working copy)
@@ -1,7 +1,7 @@
 /* Center image block by default in the editor */
 
 .wp-block-image,
-.wp-block-image > div {
+.wp-block-image > div:not(.components-placeholder) {
 	text-align: center;
 }