The new A12 Classic theme has a big clock or small clock on the lockscreen. However, once you chosen the big clock, youre unable to go back to the small clock.
Is this what was intended?
This might actually be by design from Google
To be honest Google really messed up a lot in the UX department, on pixels you cant even their widget on the homescreen, can't even switch fonts. At least ASUS adressed this.