[Block Library - Quote]: Restrict single block transforms to specific…

… blocks (#44106)

packages/block-library/src/quote/transforms.js

@@ -64,6 +64,16 @@ const transforms = {
 			isMultiBlock: true,
 			blocks: [ '*' ],
 			isMatch: ( {}, blocks ) => {
+				// When a single block is selected make the tranformation
+				// available only to specific blocks that make sense.
+				if ( blocks.length === 1 ) {
+					return [
+						'core/paragraph',
+						'core/heading',
+						'core/list',
+						'core/pullquote',
+					].includes( blocks[ 0 ].name );
+				}
 				return ! blocks.some( ( { name } ) => name === 'core/quote' );
 			},
 			__experimentalConvert: ( blocks ) =>