Icelandic Arnalds Confusion

Unless I am losing the plot, has there been a line up mix up between Olafur and Olof Arnalds? I was looking forward to seeing Olafur but now see that a lady called Olof (Olafurs sister perhaps?) has taken his place on the walled garden stage plus the spotify track and bio has changed.

Could anyone shed some light on this please?

from wiki:

Ólöf Arnalds (born 1980) is an Icelandic singer/songwriter and indie musician who has been active within the Icelandic music scene for quite some time. Apart from her own music and being a touring member of múm since 2003, she has cooperated with bands and artists such as Stórsveit Nix Noltes, Mugison, Slowblow and Skúli Sverrisson.

Ólafur Arnalds (born 3 November 1986) is a multi-instrumentalist and producer from Mosfellsbær, Iceland.[1] Ólafur Arnalds mixes strings and piano with loops and edgy beats crossing-over from ambient/electronic to pop.[1] Ólafur was a drummer of hardcore/metalbands Fighting Shit and Celestine, as well as others.