Hi James,
Thank you for opening a new topic.

You can remove other code and use the following code to force crop

function buddydev_enable_crop_for_cover_image( $args ) {
	$args['crop'] = true;

	return $args;
}
add_filter( 'bp_after_attachment_cover_image_edit_image_parse_args', 'buddydev_enable_crop_for_cover_image' );

This will not show any user interface. What it does is forces BuddyPress to crop images to the registered dimension instead of resizing the image.

In case you want to set a custom height/width for the cover and not use the default by BuddyPress, you can use the following code too

function bd_set_xprofile_cover_image_dimension( $settings = array() ) {
	$settings['width'] = 800;
	$settings['height'] = 400;

	return $settings;
}
add_filter( 'bp_before_members_cover_image_settings_parse_args', 'bd_set_xprofile_cover_image_dimension', 100, 1 );
add_filter( 'bp_before_groups_cover_image_settings_parse_args', 'bd_set_xprofile_cover_image_dimension', 100, 1 );

Please change the width/height as needed.

And lastly, you may want to remove the default notice by BuddyPress. to do that, Please add the following code.

add_action( 'bp_loaded', function () {
	remove_action( 'wp_ajax_bp_cover_image_upload', 'bp_attachments_cover_image_ajax_upload' );
} );

Please try uploading an image and cover and check if the image is cropped to correct dimension or not?

Regards
Brajesh