[henrikschroder]

To perceive time as a dimension is useful

If you want to do space-time calculations, yes.

because it helps you realize you actually perceive four dimensions the same way a flatlander perceives three

Absolutely not. We perceive time as time and space as space. The concept of spacetime does not help us understand or visualize higher dimensional spaces at all. It only confuses the issue, which is exactly the original complaint against the video this whole discussion is about.

Edit: One more example: Can you visualize the difference between a 3D cube moving in time, and a 4D cube moving in the 4th dimension? If you project the 4D cube down to 3D, it will look like a double cube that twists itself inside and out, but the 3D cube moving in time will just look like a 3D cube. Spacetime does not help you understanding 4D space.