Why do different methods for determining the temperature of the sun’s surface give slightly different results?

There are two main reasons:
1) the distribution of energy in the spectrum of the Sun differs from the distribution of energy in the spectrum of an absolutely black body;
2) different methods, strictly speaking, give the temperature of different layers of the solar atmosphere.

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.