Misleading first progress bar when installing a flavor

The first progress bar when installing the standard flavor is really misleading: it instantly goes to 75% and then it remains stuck there for a (perceived) long time (see screenshot)

I think that it's related to a computed number of steps and the last step is very long since it involves resolving the extension. However even when knowing it, it's always a bit painful to not see this bar moving and feels a bit like "Windows 95 file copy"

Note that once this step is finished, clicking on "continue" displays a progress bar acting more naturally (I guess that's because we know then the number of things to do).