What it looks like to me is Firebase put more emphasis on the technical test. If you keep your exact numbers, except change the test pass rate to 25%, then you come out with 62-63 offers, which, by the argument you reference, would mean Firebase was 56% more selective.
That makes sense to me, because a smaller company needs to filter out as many people who couldn't possibly get hired at earlier stages, since the later stages are even more time intensive than code reviewing the technical test.
That makes sense to me, because a smaller company needs to filter out as many people who couldn't possibly get hired at earlier stages, since the later stages are even more time intensive than code reviewing the technical test.