The browser tab shows the guide's own logo
A guide's tab icon, and its icon on a phone's home screen, are now drawn from the logo you upload under Theme docs, on a small tile in the guide's color scheme, in place of the Inference Bureau mark. A theme performance report, which shares the guide's look, takes the same icon. A guide without a logo keeps the mark, on the same tile.
The tile takes the logo of the scheme the guide opens on: the dark logo on a dark tile, the light one on a light tile, and either when only one is uploaded. That keeps a light logo visible on a light tab bar, where it would otherwise vanish. The icon follows a new logo within an hour.
More in Theme documentation.