Dex does not properly create field sets

[rileydog]

What I did:
in dex: create new CT; add fieldset; click on tab for this new FS; and add a field. Repeat for second FS.
I tested by creating a new instance of the CT. The fieldsets did not display properly.
Then I reviewed the schema, Below is the schema: Note both FS are empty.

For complete discussion please see here (note: discussion on this issue is at the end of the discussion):
https://community.plone.org/t/dexterity-cts-dont-display-tabs-created-using-field-sets/5740/17

<?xml version="1.0" encoding="utf-8"?>
<model xmlns:form="http://namespaces.plone.org/supermodel/form" xmlns:i18n="http://xml.zope.org/namespaces/i18n" xmlns:lingua="http://namespaces.plone.org/supermodel/lingua" xmlns:marshal="http://namespaces.plone.org/supermodel/marshal" xmlns:security="http://namespaces.plone.org/supermodel/security" xmlns:users="http://namespaces.plone.org/supermodel/users" xmlns="http://namespaces.plone.org/supermodel/schema">
  <schema>
    <field name="field_added_to_fs_1" type="zope.schema.TextLine">
      <description>this should be inside FS 1</description>
      <required>False</required>
      <title>field added to FS 1</title>
    </field>
    <field name="inside_fs_2" type="zope.schema.TextLine">
      <description />
      <required>False</required>
      <title>inside FS 2</title>
    </field>
    <fieldset name="field_set_one" label="field set one" description="this is a fieldset" />
    <fieldset name="fieldset_2" label="fieldset 2" />
  </schema>
</model>