A spinning generator is not outputting 10x it's rated current over any significant amount of time. You can only add so much steam or fuel to a turbine, and the rotor has a lot of inertia, but not enough to account for 10X its rated capacity for a second. The electrical switchyards would trip nearly instantaneously if it's connected plant output 10X its rated input.
A properly running grid with spinning generators never needs the 10x rated current. More importantly, oscillations are dampened by the rotating masses.
Although I’m hardly an expert on power lines(my factory produces HV switchgear), a 1s short circuit current rating of 10x(actually more) is normal, standard to IEC norms.
