\addlyrics always adds to first staff

[Arjan Bos]

When using \addlyrics more than once, it sets the second lyrics to the 
first staff. Is this a design decision?

When I have two Staffs and I like both of them to have lyrics I thought 
I'd simply do:
\score {
  \StaffGroup {
    <<
      \new Staff { \sopranoMusic }
      \addlyrics { \sopranoLyrics }
      \new Staff { \altMusic }
      \addlyrics { \altLyrics }
    >>
  }
}
But then the \altLyrics just follow the soprano music, instead of the 
alt music, as I would have expected. It doesn't matter if the 
\addlyrics{} is inside or outside the \new Staff{} braces.

Should I report this as a bug?

Kind regards,

Arjan Bos

---
It was funny how people were people everywhere you went, even if the 
people concerned weren't the people the people who made up the phrase 
"people are people everywhere" had traditionally thought of as people. 
And even if you weren't virtuous, as you had been brought up to 
understand the term, you did like to see virtue in other people, 
provided it didn't cost you anything.

-- (Terry Pratchett, The Fifth Elephant)