> - Characters starting with the vowel i sound more an e. Therefore, "to invite", 請 (cing2), sounds more like ceng2, and "to hear/listen", 聽 (ting1), sounds more like teng1. As a Cantonese speaker, I love the effort here! However, the above isn't correct. This is an example of vernacular vs. literary pronunciation, and 請 has both pronunciations, depending on context. For instance, 請 is ceng2 when used as the verb "to…
And you are definitely right about 懶音. They are both explained in the same section not because they are the same thing but because they are both modifications occuring for the sound pronunciations.