string swoops in Mahler's 9th Symphony

So I have been listening to a few recordings of Mahler's 9th symphony. This recording though

http://www.arkivmusic.com/classical/album.jsp?album_id=102070

has an especially interesting interpretation of the final movement. I have never heard any other recording like it. The final adagio, the strings slide up and down, creating a swooping effect, to reach their notes. I really like it, but I am just confused as to who took the liberty to do this? Is this normal in Mahler 9 recordings?

I don't know the symphony all that well, nor is it one that I have a score for, but my guess is that it's in the score and that this particular director really asked the strings to bring it out. Mahler was very fond of putting portamento marks in the strings, especially for large leaps of interval.

That, or it's a result of the Cheap Fosamax.