Polylang possible fix for 'Missing argument 2' error

I’ve come across a couple of errors from Polylang in combination with another plugin, in my case Profile Builder Pro v.2.1.9.

Warning: Missing argument 2 for PLL_Admin_Sync::add_meta_boxes() in [MY_SERVER_PATH]\wp-content\plugins\polylang\admin\admin-sync.php on line 46
Warning: Missing argument 2 for PLL_Plugins_Compat::cft_copy() in [MY_SERVER_PATH]\wp-content\plugins\polylang\include\plugins-compat.php on line 226

After googling for these errors I found that they were more common and not limited to my specific case/plugin. I looked at the code and found that both mentioned functions need the same parameters.

@param string $post_type unused
@param object $post current post object

What strikes me is that the first parameter $post_type is stated as ‘unused’. Is this because of legacy? I’d think an unused parameter could be removed completely, or if it’s a optional parameter, moved to the end of the argument list with a default value.
My guess is that these other plugins send the $post parameter, but it gets handled as the $post_type parameter while post is still missing.

The following edit in both functions made the errors go away, but is this an actual fix or am I likely to break stuff?
– giving the second parameter a default value of false
– using $post_type as $post when only one parameter is given

function [FUNCTION_NAME]($post_type, $post=false) {
  if ( !$post ) $post = $post_type;
  [...]

https://wordpress.org/plugins/polylang/