Platform Builder doesn't need to have all game creating tools or we can take a break from PB to make something more complicated things which have been made for creating things from scratch or nothing.
And I think PB has a very proper physics. Some people said that they prefer "perfect" physics like for Hello when we used MB a lot but when I played games made with Hello engine it was very difficult for me to control the player and it felt far from being perfect next to a lot of other games. Those physics are somehow so sudden and fast and too sensitive. At the same time, if it is hard to beat the MB game then it was not for sure because of physics.
I think that the perfect physics may be translated improperly also because of what we have used to handle more often. Let's just call physics proper if it has no much bugs nor glitches! And let's be honest, PB physics is very decent although every system has some undetected issues.