The question occurs, if the turbines are one-way only, why not stick two turbines in, one for in, the other out?

PV is globally accepted to be the cheapest means of generating electricity and it has been for some time. The storage required to make it all work is, however, another matter.

Two turbines was my initial thought. Maybe too difficult for them.

This is very interesting. Considering that the usual complaint is that wind power only works when there is wind, you can't say the same for waves - there will always be waves. It's not without it's own problems with the tide so not totally universal. It doesn't look nice and has obviously not been designed to fit in but I'm sure it could better designed to fit the scenery if that was part of the brief.
I like the idea for a turbine in and a turbine out. I'm sure they've thought about this.

Better to harness the tides right next to all coastal cities— they rise and fall 26 feet every day — powered by the moon — no need to despoil and the energy is right where it is needed — no transport costs..

The OWC is an artificial blowhole consisting of a chamber that is open underneath the waterline. As waves pass the OWC, the water rises and falls inside, forcing the air to pass by a turbine at the top of the chamber. This turbine generates electricity.
Previous OWC technologies have all been bidirectional. The WSE technology, however, operates unidirectionally. This results in the WSE turbine being simpler, more robust and reliable, and exhibiting a higher energy conversion efficiency. The only moving parts in the technology are the turbine and bespoke valves, all of which are well above the water line. There are no moving parts in or below the water.

I suspect the only reason these alternative sources are reaching coal energy prices is because of all the restrictions and penalties placed on coal energy.

So none of your read how he said,”... that the complexity of bidirectional turbines makes them less efficient than a simple, single-direction turbine like this one.”

The best part about generating energy with waves is that it is steady, no days when energy isn't generated on account of a day without sun or wind.

Adding a second unidirectional turbine would probably reduce overall efficiency, because it would reduce flow for the other turbine.