Clone As Multiple Feature Doesn't Work With Taxonomy Advanced Field

I'm trying to make a field of type taxonomy advanced with similar settings to the below:

'id' => 'custom_taxonomy',
'name' => 'Custom Taxonomy',
'type' => 'taxonomy_advanced',
'taxonomy' => 'custom_taxonomy',
'clone' => true,
'clone_as_multiple' => true,

When using clone as multiple, the data is saved to the database as a serialized array when it should be saved to multiple rows instead. Furthermore, the edit page only displays the first of the three taxonomy terms that were selected:

a:3:{i:0;s:3:"670";i:1;s:3:"667";i:2;s:3:"689";}

When clone as multiple is disabled, the edit page displays all three of the selected categories - cloning works as expected.

Related to this, if I manually create three rows for this taxonomy advanced field when clone as multiple is enabled, then only the first row shows up on the edit page.

To summarize:
- The "clone as multiple" feature doesn't save taxonomy advanced field data in multiple rows.
- The "clone as multiple" feature only displays one row of data belonging to taxonomy advanced fields.