Totally up to the owner, but as he said he's not done
But I wouldn't have used 2x4's, I would add 2x4's for the vertical bracing instead of 3/4 poplar (at least that's what it looks to me)
Wouldn't use the galvinized fastners as they will rust eventually even under a coat of paint.
I wouldn't have laid the 2x4's flat on the bottom (very little strenght this way) instead would have used 3/4 ply under the whole area to distribute the area evenly.
I would also add a crossbrace at say 45 to provide the tnak from leaning or the frame from racking. I didn't do this with mine but mine is attached to a wall and if it pulls away from that I've got bigger problems.
As for the woodworking looks good, I'm assuming he's going to paint the wood, if that was the case I wouldn't have used the poplar but maybe pine, good choice on the poplar though as it will hold up better.
That's it for now
Like I said I don't mean to bash the guy, but that's an incredible amount of water to go surfing through the living room at 3:00 AM
Just offering encouragement not critizing, but it might seem that way, sorry if it does A_Thrice