There was a study done on the advantage of the wind up giant (tong fei) as opposed to doing the regular giants and..the outcome was that there isn't any advantage..well in that it (the tong Fei) generagates any more angular velocity (which is the key to giants usefullness), but it is less energy taxing. Meaning that at the end of a routine when you are just tired as hell this giant does have a distinct advantage.
It could also have a psychological advantage to it. however i do think that it is usually leads to early releases.
Lately though there is a growing trend in WAG gymnastics to try and do a similar technique..by pushing the toes over the low bar rather then the under. Is it good? well really if you can time it right i dont think it makes an real difference. At the end girls are doing layout layouts super thight and nice (eg McCool)..double doubles layout (eg Johnoson, and McCool) and even tripples (forget names.. didnt Shantessa Pama do it?). These are pretty much the same dismounts as MAG, with the disadvantage that the UB High Bar is lower then the MAG HB...and they have a low bar to worry about, which means that your bail has to be optimised to get really sweet dismounts.
Essential if a WAG gymnast tried to do a Tong fei giant, she does run the risk of hitting the low bar. However i think the bigger limitiation to it for WAG is that
1- girls at that level/age are just not powerfull enough.. If you look at the MAG and WAG and compare the velocity of giants, tap you will notice a considerable difference
2- There is a tendancy for people who do use this technique to go further away from the bar and be lower then if you did standard giants into your dismount..which for WAG would just not work
Example
Aljzas Pegan regualar giant into dismount = tripple back pretty high almost no cowboy tuck. and lands safely away from the bar but doesn't go flying.
Vlasios Maras tong fei giant into double double = goes flying and his peak height is lower then the Pegan.
Even though the skills are different they both requires relatively equal amounts of Angular velocity to make it around (however i need to ref to books to be sure on that).
And also these are just two contasting cases (not enough to really shock the world)..but if you do look around i think you will notice that there is a pattern with that.
i short... i think that the Tong Fei is not of any real advantage to WAG, and it is not even a huge advantage in MAG either.. you may think it, but mechanically speaking when wanting to generate angular velocity the standard giant wins.