AD8629 as a current sense


i want to use AD8628 as a current source .

in it's datasheet page 19 it said that : "As long as the rate of change of the current is not too fast, an auto-zero amplifier can be used with excellent results. "

whats the problem with too fast changes of current?

how much does it mean by too fast?

in my application i want to use AD8629 as a current sense for a closed loop feed back of a current source for exiting a coil with a pwm wave. my pwm frequency is about 10 HZ but it has sharp edges. can the sharp edges of current excitation impact my system based on the mentioned note of the datasheet?