He already answered you:
Seems pretty clear to me.
It’s no more an “indefinite” contract than the GwG stewards. To wit: the GwG doesn’t get dissolved. It’s a PERMANENT working group that only rotates stewards via elections. And so, as long as the GwG exists so too does the secretary that is hired to serve in that role. And thus, unless and until the GwG take a vote to change the secretary, that role remains filled. Hence the reason that if the GwG were to be dissolved as per AIP-466: Proposal To Close Non-Essential Working Groups so too would the role since it’s funded by the GwG budget. In other words, the role, if not vacated along with the GwG, would essentially be automatically defunded.
Hope that’s clear now.