are you serious? do you know what 50/50 weight balance is?! thats whats most cars try to achieve and thats what the ae86 has. anyone can drift a s-chassis but not everyone can drift an ae86. the ae86 is a very potent car and the only reason you dont see a huge fanbase is that theres fewer of those around than s-chasis cars. not to start a debate but most tuners will pick a mint ae86 over a mint s13 7 times out of 10. the ae86 is what started the drifting trend in japan. in fact it cost more in japan than a r32 gts-t, s13 silvia just for the fact that its a better overall car. if your asking how realistic initial d is, they actually consult keichi tsuchiya on the whole anime. that anime is very loosely based on how he started drifting. so it is somewhat realistic.
p.s. did you want the truth why you see so many s-chasis at drift comps? you can easily buy one for cheap, relatively cheap to modify, more aftermarket support, very easy to drift.