Yeah,yeah Although the accent has disappeared in some places, there are also many places that can be distinguished and have a very clear pronunciation. For example ཁེ།and ཁེད། ཁྱོ། and ཁྱོས། With different pronunciation.

cuz the Tibetan alphabet was established in the 7th century. While the actual value( and that is how people actually say these words)of these words changed over time, the literary spelling remained the way they were in 7th century. Thus, these ས་and ད་ were pronounced when the spelling system first established (actually some consonant clusters still remain in some Tibetan dialects, for example in Amdor region), but as the language change over time, these ས་and ད་got lost in oral language. Analogous phenomena can be seen in English and other alphabetical languages which has a long history of writing. For example, in English the word “light “ is not pronounced in the way its spelling indicates.