This is definitely not the place to go into the details of brailling. That can be better left to the specialists. It is only necessary to realise that a music braille version of a piece of music, using standard codes which can be read by any proficient reader, may in fact be difficult because the only edition available is in an unfamiliar layout format. Most people are, when the need arises, able to overcome the differences in layout. It is very difficult to standardise these formats.
Different music demands different presentation.
In principle a music piece is not normally brailled again because a reader prefers another format. In 1989 the World Blind Union Music Braille Committee decided that it was time to up-date the existing manual and to take steps to bring the major libraries together. Together these four music braille libraries decided to build a central catalogue representing their holdings. As anyone who has been involved in constructing a Union Catalogue will know, there are lots of things that have to be agreed upon. It was a natural decision that none of the participating libraries would be expected to alter their own catalogue.