Comment 2 for bug 543033

The screen should have been cleared by syslinux on exit from gfxboot, which should have been almost immediately after you pressed Enter and quite a while before the system got round to displaying the splash screen. I don't know why this didn't happen in your case.

ubiquity cannot be involved here - none of its code runs until quite a bit later, and the changelog entry you found is referring to a different bit of user interface.