Oh yeah, lol, it was that.
Well, this modified setup behaves as predicted:
void setup () {
// reset Timer 2
TCCR2A = 0;
TCCR2B = 0;
TCCR2A = _BV (WGM21) ; // CTC mode
OCR2A = 155; // zero relative
// Timer 2 - interrupt on match
TIMSK2 = _BV (OCIE2A); // enable Timer2 Interrupt
TCNT2 = 0;
// Reset prescalers
GTCCR = _BV (PSRASY); // reset prescaler now
// start Timer 2
TCCR2B = _BV (CS20) | _BV (CS21) | _BV (CS22) ; // prescaler of 1024
pinMode (9, OUTPUT);
} // end of setup
Theory: 62.5 nS * 1024 * 156 = 9.984 mS. That pretty-much agrees with measured results. In other words, a wake-up 100 times a second. Count those, and you know how much time has elapsed.