Well I travel a lot so a fixed float charger for my AGMs doesn't work as they do indeed get discharged and charged. But that is a great price and I may get one for my bench work.
In the meantime my Magnum does a good job of charging the AGMs. And no it is absolutely NOT up and down charging. It charges the batteries, brings the float down to the temperature compensated voltage. And there the voltage stays regardless of house loads, well up to 100A anyway. But then it costs more.
Magnum did make design/cost tradeoffs that I've documented.