I have to admit that I haven’t used the asset_hash in v3, but testing now on a new site the two doesn’t work.
My assets added traditionally are all updated, the one with the helper are not.
e.g. regardless the setting the following line
<%= stylesheet_link_tag "jquery.mmenu", :media => "screen" %>
produces
<link href="/en/content/css/jquery.mmenu.css" rel="stylesheet" media="screen" />
Any idea?