Does the postulate of the constancy of the speed of light imply the constancy of the direction of its propagation?

No, it doesn’t mean. Light can change its direction even to the opposite. The speed of light will remain unchanged.

Remember: The process of learning a person lasts a lifetime. The value of the same knowledge for different people may be different, it is determined by their individual characteristics and needs. Therefore, knowledge is always needed at any age and position.