XF 2.1 Template Modification Help

[Cupara]

I'm adding an admin template modification and what I'm trying to do is the example that @Chris D provides in this thread https://xenforo.com/community/threads/nested-inputs-input-disabler.160457/post-1322016

I continue to get

Option tag contains unexpected child element

but I'm not understanding I guess how this should work.

<hr class="formRowSep" />
<xf:checkboxrow>
    <xf:option name="gt_agegate"
        label="{{ phrase('gt_agegate') }}"
        hint="{{ phrase('gt_agegate_explain') }}">
        <xf:checkboxrow name="gt_ag_agegate" value="{$forum.gt_ag_agegate}" label="{{ phrase('gt_agegate_title') }}">
            <xf:option value="1" label="{{ phrase('gt_agegate_enable') }}" hint="" />
        </xf:checkboxrow>
            <xf:numberboxrow name="gt_ag_agelimit" value="{$forum.gt_ag_agelimit}" min="0" max="100"
                label="{{ phrase('gt_agegate_min') }}"
                explain="{{ phrase('gt_agegate_min_ex') }}" />
        <xf:checkboxrow name="gt_ag_mature_o" value="{$forum.gt_ag_mature_o}" label="{{ phrase('gt_agegate_m_warn') }}">
            <xf:option value="1" label="{{ phrase('gt_agegate_enable') }}" hint="" />
        </xf:checkboxrow>
            <xf:numberboxrow name="gt_ag_mature_time_o" value="{$forum.gt_ag_mature_time_o}" min="0" max="365"
                label="{{ phrase('gt_agegate_m_time_days') }}"
                explain="{{ phrase('gt_agegate_m_time_ex') }}" />
        <xf:checkboxrow name="gt_ag_banner" value="{$forum.gt_ag_banner}" label="{{ phrase('gt_agegate_banner') }}">
            <xf:option value="1" label="{{ phrase('gt_agegate_enable') }}" hint="" />
        </xf:checkboxrow>
            <xf:textboxrow name="gt_ag_banner_icon" value="{$forum.gt_ag_banner_icon}" hint="{{ phrase('gt_agegate_banner_icon_h') }}"
                maxlength="120"
                label="{{ phrase('gt_agegate_banner_icon_l') }}" />
            <xf:textarearow name="gt_ag_banner_text" value="{$forum.gt_ag_banner_text}" autosize="true"
                label="{{ phrase('gt_agegate_banner_text_l') }}" maxlength="1000"
                hint="{{ phrase('gt_agegate_banner_text_h') }}" />
    </xf:option>
</xf:checkboxrow>
<hr class="formRowSep" />
    $0