Gutenberg InnerBlocks with ACF Blocks - How to enable multiple buttons?

I'm trying to use Gutenberg's InnerBlocks with ACF Blocks in my allowedBlocks I have [ 'core/heading', 'core/paragraph', 'core/buttons'] In my 'core/buttons' block I'd like to allow multiple buttons, but it only seems to enable one.

My block template is as follows:

[
    [
         'core/heading',
         [
             'level'       = 3,
             'placeholder' = __( Add Heading..., THEMENAME ),
             'align'       = 'center',
             'className'   = 'has-text-align-center',
         ],
     ],
    [
          'core/paragraph',
          [
               'placeholder' = __( Add paragraph text..., THEMENAME ),
               'align'       = 'center',
          ],
    ],
    [
          'core/buttons',
          [
               'align'       = 'center',
          ],
    ],
] 

Additionally the align 'center' doesn't seem to work for this block.