Seems to me that IRC §911 makes it pretty clear. Any income received after the year after the service was rendered does not qualify for the exclusion. Non-qualified stock options are normally taxed when granted.
If he received stock options while abroad, during the appropriate time period, he doesn't have to recognize income during that year.
But I'd think that the exclusion would not apply to income that would be taxable either on the exercise or sale of the option, particularly if it occurred after the two year period.