No doubt one of the more unusual posts I’ve read, and maybe that’s why you’ve had no responses as yet.
Here goes……as you expected that the sprinkler problem would have been picked-up in a pre-purchase inspection I assume that those sprinklers are of the below ground gear driven pop-up variety. That being the case, most pop-up sprinklers have an adjustment to limit flow, to alter the spray area, and the ability for the nozzles to be swapped over to provide different spray patterns – just like variably adjusting a hose nozzle from a fine spray to a jet.
Even if the sprinkler’s not “fixed”, as I remember WAWA’s roster system none may be used between 9am and 6pm, so the “doctor” should have calmed and the chance of over spray reduced by the time that sprinkler use can legally commence (sorry, I forgot the forum’s no acronym rule; WAWA= Western Australian Water Authority).
Surely your neighbour would be amenable to either making those sprinkler adjustments or having them done by a irrigation contractor to make better use of WA’s groundwater resource; after all cars and lounge room windows don’t suffer from an absence of water.