It is entirely possible, website_sale.products_categories view must be edited, by removing hidden-xs parameter:

<?xml version="1.0"?>
<data inherit_id="website_sale.products" active="False" customize_show="True" name="Product Categories">
  <xpath expr="//div[@id='products_grid_before']" position="inside">
      <ul class="nav nav-pills nav-stacked mt16">
          <li t-att-class=" '' if category else 'active' "><a t-att-href="keep('/shop',category=0)">All Products</a></li>
          <t t-foreach="categories" t-as="c">
              <t t-call="website_sale.categories_recursive"/>
          </t>
      </ul>
  </xpath>
  <xpath expr="//div[@id='products_grid_before']" position="attributes">
      <attribute name="class">col-md-3 hidden-xs</attribute> <!-- remove hidden-xs from this line -->
  </xpath>
  <xpath expr="//div[@id='products_grid']" position="attributes">
      <attribute name="class">col-md-9</attribute>
  </xpath>
</data>