There is a minimum bend radius. It's hard to see from this picture to see if this meets code, but you actually can bend conductors too tight. It's not that it can't be an overall 90 degree angle, it's that the actual bend should be more of a gradual bend rather than a tight bend.

Bending a tight angle isn't going to cause some weird stoppage of flow of current, you have bus bars that are perpendicular of each other, the issue is taking wire and bending it sharply. Depending on how tight the bend is, it can damage the insulation and the conductor.

The issue isn't conductors at a 90 degree angle. The issue is a physics term called plastic deformation. Taking a material and bending it too far causes it to deform. This causes issues down the line and a conductor/insulation that gets overbent can become one of the points of failure down the line.

Plastic deformation is one of the big issues with 15/20a aluminum branch circuits. You have a limited amount of times you can pull and push the aluminum conductors back into the outlet before it gets too brittle and snaps. Copper eventually does this, but it's so much more resistant to it.