Poor install as evidenced by the odors present within the home…
Guy must be a Calder Coupling salesman…!
What is amazing about your post is that I was about to post about one myself…
It is the first one that I have seen…when that lift station kicked on while I was watching the bathtub drain…I almost shat myself as it was right next to where I was standing…
And then when I drained the upper floor giant tub it did it again and I could hear it throughout the house…the h/o was there
Any info on these types of lift stations? Does all the plumbing in the house go through them or just the “below grade” levels?
What happens if the lift station pump dies and you drain all the tubs in the house several times prior to noticing it and you flood the area? Is that a real concern?
The ones I’ve seen only are used to drain fixtures below the discharge point of the system.
The fewer plumbing fixtures on the system as possible, the better.
Water seeks its own level. Use your imagination! 
I think you have sufficient grounds for a “investigate further”.
Here comes the deal killer…