Is this true cuz i did it like 7-10 times

nah that's bs

or to the extent of my knowledge it is

There actually is a reason for that. Whenever you're working with a positive battery terminal there is always a chance that your wrench could ground out the terminal to a part of the car and cause sparks or a surge in the computer. If you remove the negative side first that threat is removed. There is no longer a continuity between the battery and the car. It's the same reason you're supposed to attach the positive cable of jumpers first and then the negative cable to an engine part and not the battery.

Batteries are extremely explosive. Way more explosive than gasoline. I had a friend who had a battery explode in his face just from connecting the cables. We had one explode in a shop I worked at many moons ago just from turning the key to start the car.

BTW, 30 mins is a bit of a myth. Once you disco the cables, hit the brake pedal, headlights etc - that will discharge the capacitors in the computer.

And DO follow MS's sage advice.

Good luck.

The computer doesn't know which cable you disconnected. All it knows is that there is no input power. From an electrical standpoint, either cable is OK to disconnect. From a safety standpoint, always disconnect the negative cable.

sorry i forgot to mention the safety part of it, i was looking at it like the first part of jrichker's post, that simply disconnecting pos lead first shouldn't harm anything (assuming you don't arc your wrench to the frame)