I recently read a bit about "grand tack" hypothesis. It was extremely interesting and it seems to reasonably well explain many features of our solar system. At the same time it supposedly is consistent with our knowledge of other planet systems, which I don't understand. What exactly happened in solar system and at which point , that is so rare out in the other systems? Combination of Jupiter/Saturn showing up at the right places and the right time? Isn't it common that the biggest gas giants appear somewhere over the edge of frost line?
We do not yet know whether our solar system is a common or rare outcome of the planetary process.
The statistical properties of exoplanetary systems are severely affected by observational biases. It is far easier to detect close-in giant planets; objects like Saturn, at Saturn-like distances from their host star, have not been found due to the limitations of the observations.
It is therefore far too early to say whether the Grand Tack model may or may not be applicable to a wide variety of exoplanetary systems. What we do know, is that something drastically different happened in the case of those systems that have a Jupiter-sized planet within an astronomical unit or so of their parent star; but these are found in only a few per cent of stars.
As an addendum, it is also the case, that despite taking 10+ years of data to establish them, there are now many cases of Jupiter-like planets in Jupiter-like orbits, though they are probably not that common. The overall conclusion at present is that the solar system does not look that unusual, although the lack of close-in planets larger than the Earth is notable (see Martin & Livio 2015).