When I tap .APK files in a file browser like ES File Explorer, I get two options: "Verify and install" with the Google installer icon and "Easy Installer". That it uses the word 'verify' makes me think it may be the same verification procedure. The less interactive Easy Installer probably skips that step.
...well I used to get two options. I'm not sure why but I tried it just now and didn't get asked. I must have checked a box saying not to ask me again.