Just to be clear, this is entirely a marketing issue, and I'm not sure any PV installer/seller does a good job explaining.
First "turbo" or "overdrive" doesn't mean that your PV inverter can produce over 7.6 kW at any time. When the sun is well aligned and the temperature is cool and your PV panels could produce more than 7.6 kW DC, your inverter will clip and limit you to 7.6 kW AC. What the 1.7 ratio means is that the inverter will handle that clipping gracefully without overloading any of the components, up to a 1.7 nominal DC/AC ratio.
The thing that is not immediately obvious is that if you want to design a system with an optimal lifetime kWh/$ (i.e. you can't improve limeftime production by spending a little less (or more) on inverters, and using that savings (or cost) to add more (or fewer) PV panels), then you will end up with a system with a DC/AC ratio bigger than 1.0. That's because inverters are not free, and the number of hours per year that PV panels will produce their actual nameplate rating (or close to it) is fairly low. So given the cost of the inverters, it makes sense to spend some more on extra PV panels so that you have less "idle" inverter capacity, even at the expense of having some "idle" PV capacity.
Once your realize that you should generally only sell and install PV systems with a DC/AC ratio bigger 1.0 if you want to be more economically optimal (assuming no other constraints like limited roof area, etc), then the question is what figure do you use to market the "size" of the system? The vendors like to use the DC size because it's a bigger number and sounds more impressive.
That's fine as long as everyone realizes that when they are getting a "10 kW" PV system, that means a system with 10 kW of PV panels, and a smaller inverter size, and that given their location it should work out on average to so many MWh of energy per year over 20 years. It doesn't mean a system that will produce as much energy as possible as any system with 10 kW of PV panels could produce at that location. Because it doesn't make sense, e.g., for Tesla to raise their prices by 5% so that they can give you 2% more energy.