What does one lose by going Eco? If you can simply reduce pulses to 1 in 10 with same performance then why aren’t all routers like that?

You need to ask the manufacturers of those routers! The only downside is that it can take longer when many devices are connected at the same time (think 30+). And that a few percent of wireless devices are not compatible with the reduced pulse frequency. Connection throughput speed and network stability are the same as with ordinary wifi routers.