have you ever seen it spelled that way? It could just be a regional lack of emphasis on the "h." I've never seen it spelled without the "h."
I've seen a lot of TZn wedding invitations (from different parts of TZ) and I've never seen it spelled that way. Maybe in Kenya they spell it that way? Where is the author from?
I think the author's originally British but she's a university swahili teacher who's spent years in Tanzania... but just to be safe I'll be saying "harusi".