Why we don't need to show a progress when capture option is off?
Because since we are not capturing output, the output of the tests can create quite a mess in the terminal and printing the progress indicator really only adds to the mess so it was decided to not print it at all (also we can't really track the correct position where to put the progress indicator because the output is not coming through the TerminalReporter, which tracks the number of characters written per line). The example shown here does not suffer from this because the tests do not actually print anything, but that's not easy to detect.
So we really should just find the bit of code which "slipped" that check and not print the indicator in that case. 😁