I believe James is correct; that this is a mistake.
The only piano roll "recording" that I know of which Mahler himself performed, is the Welte Mignon Piano rolls of 1905-1906.
They feature three short pieces "played" by Gustav Mahler himself.
They include the songs,
Ich ging mit Lust durch einen grunen Wald,
Ging heut' morgen uber's Feld,
and Das himmlische Leben from Symphony 4.
I know of no other piano roll recordings. For those unfamiliar with the piano roll recordings, although Mahler himself struck the keys that produced the piano roll recording, they are not necessarily a representation of how Mahler thought they should sound. Although an ingenious device (Mahler agreed that it was!), it required a determined effort to strike the keys very hard to punch holes in the strong piano roll paper. Thus, the artist being recorded had to concentrate on striking the keys, which left little room for indicating nuances of volume or tempi.
All the same, it is interesting to hear something performed by the hands of Mahler.
--John Haueisen