Yeah, that's really not right. In real terms and not just what people think from whatever driving experience they have. Understeer is a stable condition. Oversteer is unstable. Neutral is good, but will never happen. Neutral with limit oversteer is also unstable and even if the driver can keep it under control it is slower than limit understeer.
You guys are just thinking about terminal conditions, meaning understeer where you have zero front traction or oversteer where you spin out, but that's not what those terms really mean. Understeer is when you need to give the car more steering input than would normally be needed in a given turn. This is why the amount of steering angle needed to negotiate a turn at 25mph will be different than the steering angle needed to negotiate the turn at 50mph. This is called the understeer gradient of the car and unless something is screwed up, every car is going to have this.
There could be an oversteer gradient, but that would just end up causing a lot of problems. And just like understeer, oversteer is when you put in less steering angle than would be needed to take a turn. This does not mean you're in a full lock drift going around a bend. This will be slower through a turn at the limit of the tires because all your available traction is being used up. Once power is applied, you will be just spinning tires rather than acceleration. It can be useful in certain situations, but just because you have an understeer car does not mean that the car will never see an oversteer condition.
edit: and about the tires. I guess they really are 275s in the front. Those look a lot better on the wheels than the rears. The bulge on the rears just makes it look like it's going have sloppy sidewalls due to the wide tire on the smaller wheel. But the fronts look like it might not be as bad due to the way the tire is constructed.
And as far as comparing tire sizes without even mentioning wheel sizes, it's pointless. A 245 on a 7" wide wheel will have a totally different feel than a 245 on an 8" wheel or a 9" wheel. Not to mention the million other variables that will make different tire sizes feel different.
Tim