in instruments.xml, bracketSpan staff="2" spans too many staves, in the wrong place

I am attempting to bring the documentation for the instruments file up to date (V3.5). I have found a number of problems that may be of no importance. Each is being reported as a separate ticket.
The old documentation states
"•bracket
◦staff the starting staff for the bracket. First staff if not present.
The type of bracket to use. 0 normal bracket, 1 grand staff brace, 2 square brace, 3 line brace

•bracketSpan
◦staff the starting staff for the bracket. First staff if not present.
The bracket span in number of staves.

•barlineSpan
◦staff the starting staff for the barline. First staff if not present.
The barline span in number of staves."

It is not logical that the bracket element should have the attribute "staff" and this is actually rejected by MuseScore. I am treating this as a documentation error.

But, if you try to bracket the lower two staves of a three stave instrument, all three staves are bracketed.
The same problem does not occur with barlineSpan

1 Set instruments list 1 to BracketSpan2.xml (EDIT I got the wrong file the first time!
2 Clear instruments list 2
3 Restart MuseScore
4 Start a new score with the only instrument
5 All three staves are bracketed but the barlines only span the lower two (see BracketSpan.png)