Orthoepy and Writing

It is considered that orthoepy deals with pronunciation variants, where having the same phonetic position, the phonemic or sound composition of the morpheme varies, e.g. bulo[sh]naya – bulo[ch]naya; p[o]et – p[u]et. The category of variation is the main category of orthoepy. However, it is very heterogeneous and includes different phenomena: 1) cases when the same morphemes or word forms can be pronounced differently; 2) cases when there is no possibility of different pronunciation in specific words, but there are combinations of letters that can be pronounced differently in different words under the same phonetic conditions; 3) cases when the word has letters whose usual meaning in this position does not correspond to the pronunciation of the word. So, what do three different situations that linguists traditionally, based on their intuition, combine under one "orthoepical roof" have in common? There is a factor that allows you to link all three of the above mentioned situations – all morphemes that are attributed to orthoepic variation and therefore need orthoepic commentary are written in the same way, despite the fact that they allow differences in phonemic and phonetic composition.