From my (small) experience in the wet in the 86, it does a great job to utilise all the narrow stock tyres grip. At the same speeds with the same skinny tyres on an SW20, it would be understeering then oversteering.
Front and rear tyres are also the same sizes.

so a hot hatch comes with 215/45 and has 200hp.. why would this car need more tyre than that? same power?

because I would like to think the chassis design in this car is much better than a hot hatch and could benefit from/exploit a wider tyre

Don't forget about the steering feel. The wider you go with your front tyres the less intimate your steering feel will be.

Pretty sure the gts gets a larger wheel and wider tyre than the gt.

Since when has GT been base model?

Kinda like when I had 'gold' tickets to a concert.

"Oh you want to be able to actually 'see' the band? Sorry you only have gold seats, you needed diamond encrusted platinum chip level 3 tickets for that..."

The GT gets 205s (6.5" rim)
The GTS gets 215s (7" rim)
 
GT is the base model for the 86...its not a SW20 lol

Yeah but 'GT' as 'Grand Tourer' was always used as the ducks nuts model, not entry!

well because it has a good chassis - it doesnt need to cover its defficiencies with a big grippy tyre.
 
it can get the job done with just a 215..
 
put 255s on it and it will be like glue.

drove both auto and manual today.,..
 
auto is amazing.. best auto i have ever driven.. i wouldnt mind the auto actually.. i wish i could have both.

Saw a black one yesterday as I was driving along in my sister's car...pulled the longest jaw dropping face haha. The guy face was like "thanks man" and then vrooom!!
I need my car back