iTerm 2 behaves weirdly in macOS

• iTerm2 version: Build 3.1.12
• OS version: macOS High Sierra 10.13.6
• Attach com.googlecode.iterm2.plist here (drag-drop from finder into this window)
• Debug logdebuglog.zip
• Screen capture video: youtube.com/video/mbbEViOS5Kg (without debug log); https://youtu.be/tiG7WYLbT5Y (corresponds to the attached debug log)

Detailed steps to reproduce the problem:

1. Install fish with brew
2. Install iTerm2
3. Change the dark theme to light theme, and change command to "/usr/local/bin/fish"

What happened: It does not automatically enter "alternate screen mode" if less/man/similar commands are run, and it seems like fish cannot overwrite contents on the screen.

What should have happened: Fish can display whatever it wants on the screen. iTerm2 will enter "alternate screen mode" if less or man is run.

This issue is also posted on superuser a while ago (by me, but no one had helped me yet): https://superuser.com/questions/1602794/iterm-terminal-emulation-is-weird