Wordpress bug?

import assign from 'lodash.assign';

const { __ } = wp.i18n;
const { registerBlockType } = wp.blocks;
const { InspectorControls } = wp.blockEditor;
const { Component, Fragment } = wp.element;
const { RangeControl } = wp.components;

wp.hooks.addFilter(
	'blocks.registerBlockType',
	'elder/thicknessAttribute',
	settings => {
		if(settings.name === 'core/separator') {
			settings.attributes = {
				...settings.attributes,
				elderThickness: {
					type: 'number',
					default: 1,
				},
			};
		}
		return settings;
	}
);

wp.hooks.addFilter(
	'editor.BlockEdit',
	'elder/thicknessInput',
	wp.compose.createHigherOrderComponent(
		BlockEdit => props => {
			if(props.name === 'core/separator') {
				return (
					<Fragment>
						<BlockEdit {...props} />

						<InspectorControls>
							<RangeControl
								label="Thickness"
								min={ 1 }
        						max={ 10 }
								value={props.attributes.elderThickness}
								onChange={nextRel => props.setAttributes({elderThickness: nextRel})}
							/>
						</InspectorControls>

					</Fragment>
				);
			}
			return <BlockEdit {...props} />;
		},
		'withelderThicknessInput'
	)
);

wp.hooks.addFilter( 'blocks.getSaveContent.extraProps', 'elder/rel', ( element, block, attributes ) => {

	if(block.name === 'core/separator') {
		if(attributes.elderThickness) {
			assign( element, { style: { 'borderTopWidth': attributes.elderThickness } } );
		}
	}

    return element;
} )