I saw this video on YouTube in which two balls slide down on different inclines.

The part which confused me was the one at 2:00 seconds. I couldn't understand the physical reason for why the two balls hit the bottom at the same time ?

If we drop two balls from different heights they do take different time to come down . But here they are coming simultaneously.

One reason which I thought could be that the velocity gained by the balls is proportional to length of the incline but I am not sure and couldn't digest it .

A physical reason would be more appreciated than a mathematical one.

Edit : It is written in the comment section that it is designed that way so that the balls reach the bottom at the same time .

But I still couldn't understand how does that structure of the incline actually affects the timing. What's the physics behind that ?