Try moving stabilization to after the filter is run

src/wp-includes/class-wp-block-type.php

@@ -579,29 +579,6 @@ public function set_props( $args ) {
 			}
 		}
 
-		// Stabilize experimental block supports.
-		if ( isset( $args['supports'] ) && is_array( $args['supports'] ) ) {
-			foreach ( $this->stabilized_supports as $feature => $mapping ) {
-				if ( isset( $args['supports'][ $feature ] ) ) {
-					if ( is_array( $mapping ) ) {
-						foreach ( $mapping as $old => $new ) {
-							if (
-								isset( $args['supports'][ $feature ][ $old ] ) &&
-								! isset( $args['supports'][ $feature ][ $new ] )
-							) {
-								$args['supports'][ $feature ][ $new ] = $args['supports'][ $feature ][ $old ];
-							}
-						}
-					} elseif (
-						is_string( $mapping ) &&
-						! isset( $args['supports'][ $mapping ] )
-					) {
-						$args['supports'][ $mapping ] = $args['supports'][ $feature ];
-					}
-				}
-			}
-		}
-
 		/**
 		 * Filters the arguments for registering a block type.
 		 *
@@ -612,6 +589,11 @@ public function set_props( $args ) {
 		 */
 		$args = apply_filters( 'register_block_type_args', $args, $this->name );
 
+		// Stabilize experimental block supports.
+		if ( isset( $args['supports'] ) && is_array( $args['supports'] ) ) {
+			$args['supports'] = $this->stabilize_supports( $args['supports'] );
+		}
+
 		foreach ( $args as $property_name => $property_value ) {
 			$this->$property_name = $property_value;
 		}
@@ -674,4 +656,38 @@ public function get_uses_context() {
 		 */
 		return apply_filters( 'get_block_type_uses_context', $this->uses_context, $this );
 	}
+
+	/**
+	 * Stabilize experimental block supports. This method transforms experimental
+	 * block supports into their stable counterparts, by renaming the keys to the
+	 * stable versions.
+	 *
+	 * @since 6.7.0
+	 *
+	 * @param array $supports The block supports array from within the block type arguments.
+	 * @return array The stabilized block supports array.
+	 */
+	private function stabilize_supports( $supports ) {
+		foreach ( $this->stabilized_supports as $feature => $mapping ) {
+			if ( isset( $supports[ $feature ] ) ) {
+				if ( is_array( $mapping ) ) {
+					foreach ( $mapping as $old => $new ) {
+						if (
+							isset( $supports[ $feature ][ $old ] ) &&
+							! isset( $supports[ $feature ][ $new ] )
+						) {
+							$supports[ $feature ][ $new ] = $supports[ $feature ][ $old ];
+						}
+					}
+				} elseif (
+					is_string( $mapping ) &&
+					! isset( $supports[ $mapping ] )
+				) {
+					$supports[ $mapping ] = $supports[ $feature ];
+				}
+			}
+		}
+
+		return $supports;
+	}
 }