shortcode is applied before autop — Editor-widget in 1.8.2
bug-reportpluginplugin-widgets-bundle · By Volkmar Kantor · 8 years ago · Reply by Volkmar Kantor 8 years ago
WordPress applies the auto-p BEFORE it applies the shortcode. The editor-widget applies the shortcode first, so the the auto-p is applied on the ready rendered shortcode-output.