https://twitter.com/bgardner/status/1407843151109316609

block-styles-loop.php

<?php

$block_styles = [
	'core/button' => [
		'fill-white'    => __( 'Fill White', 'frost' ),
		'outline-white' => __( 'Outline White', 'frost' )
	]
];

foreach ( $block_styles as $block => $styles ) {
	foreach ( $styles as $name => $label ) {
		register_block_style( $block, [
			'name'  => $name,
			'label' => $label
		] );
	}
}