It doesn't seem that this would exactly by 'worthy' of taking up time at the inquest.. but could it be that this fellow was one previously/historically/occasionally used by FGM to help with odd repairs/maintenance around the house, but for whatever reason (which he might testify to), he was not available in mid September 2014, and hence FGM's seeking someone else?I don't know why Deck Man has been called to the inquest (he's named by News.com.au, 18 July 2019). Someone with the same name (GO) regularly advertised in Kendall's community newspaper as a provider of services including electrical, plumbing, carpentry, cleaning, lawn mowing, and so on. See page 10 of The Kendall Chronicle, 05 Sep 2014 (a PDF).
According to Reverse Australia Directory, the address for the landline number shown in the advertisement was residential land in Logans Crossing, last found June 2015.
I haven't seen any reason to suppose any of this is related to William's disappearance. Maybe the Coroner has questions about the house or property maintenance?
But 'why' BS was called by FGM instead of someone else, doesn't seem important enough, when there are SO many questions. Someone earlier suggested that perhaps he could testify to the fact that there were no trap doors or whatever, in the deck? (Not that such a thing has ever been suggested, that I am aware of?) It is a mystery, but time is flying and we'll soon find out why this man is on the list!