Lock screen horizontal layout bug on iPhone SE

I just upgraded to iOs 11.4, but the same issue is present on 11.3.1.

Here are steps to reproduce.

1. Settings - General - Reset All Content And Settings

2. Process basic steps to initialize phone and see homescreen.

3. Settings - TouchID & Passcode - Require Password - After 1 hour

4. Run Messages app.

5. Rotate phone to make screen has horizontal layout.

6. Press power button shortly to turn display off.

7. Press power button shortly to turn display on.

Expected result: lockscreen oriented vertically.

Current result: lockscreen oriented horizontally.

On iPhone SE horizontally oriented lockscreen should not appear in any case, shouldn't it?

Please don't tell me to lock phone screen orientation. I want to use both horizontal and vertical orientation.

But I think that lockscreen should not be oriented horizontally on iPhone SE and it's a bug.

As far as I did full reset, it looks like it is the bug of firmware, not some 3d-party applications or current device.

Please advice.