How can the same engine meet strict emissions if all they did was increase compression .10 to .50?

You did not provide the vehicle information YMM (year make model) of the vehicle in question, but the compression has very little to do with it! What matters is the amount of Catalyst inside the shell of the Cat's and the ( fuel and ignition maps, and warm-up efficiency of the engine, Remember compression, the higher it is, the more the NOX (oxides of nitrogen) goes up!

Changing compression ratio may actually help improve tail pipe emissions, what it is causing the engine to do is compress the air fuel mixture even more before combustion and gets a better more complete fuel burn, to get more power as a rule however too much compression is bad too, because it can actually cause a horsepower loss and severe pre ignition issues if it gets around 14 to 1 on a gasoline engine.

A mild increase of .1 or .5 though on those engines will get more HP and may increase efficiency.