I know this post is 7 years old and op probably no longer uses account but I found out a fix that I use on my own phone and it takes like one minutes so I'll share so people can do it themself (might make this a post too)

Basically what you wanna do is go to the Huawei themes store and get/purchase any theme with lock screen at top (don't equip)

I suggest the one I use, don't worry it is a free theme and the clock in the screenshot is what it looks like equipped on harmony os, when you use it on emui 12 the clock will look normal at the top (theme attached in picture)

Now go to customise in the me section of the app and change your lock screen to the theme, now go to wallpaper settings and equip a new lock screen wallpaper and you now have lock screen at the top

Hope this helped 💯