pm_update_packages() does a risky drush_drupal_cache_clear_all()

I did an updatecode from views-6.x-2.0 to current. Toward the end, I got a fatal error: Call to undefined function views_microtime(). This fatal call was kicked off by the drush_drupal_cache_clear_all() at bottom of pm_update_packages(). We should do this clear in backend process?