Why phone encryption without screen lock is possible under Marshmallow? Since phone encryption is irreversible, I'd like to ask before applying it to my phone for the first time.

I have a slide-screen unlock set under my Moto E3 / Android 6.0 Marshmallow. No PIN, no pattern. How it is possible that my phone / Android allows me to encrypt my phone in this situation?

Here are all the warnings I can see.

First screen warns me that:


I need to power up my battery to something around maximum,
I need to connect my phone to charger,
phone encryption takes 1+ hour.


Second screen warns me that:


phone encryption is irreversible,
phone encryption takes 1+ hour.


But, on both screens I can tap Encrypt Phone button without any problems.

What am I missing? Shouldn't I be rather warned that phone encryption is not possible in my case, because I failed to set PIN-lock or pattern-lock for my screen / phone? Shouldn't Android 6.0 rather disallow me to continue with phone encryption in this case?
I have a Galaxy S5 (Android Marshmallow), and when I hit the encrypt phone button, my phone stopped me and forced me to have a password or pin in order to continue. If you use finger print or face recognition, you will need to enter the password or pin on device restart. So the answer is Yes your phone will disallow you from continuing with phone encryption without a password or pin, your phone will just ask you nicely for a password as a part of the encryption process rather than send you back into the settings to make a password.