Timing drift when interrupts disabled

main.ino

void setup() {
  pinMode(D4, OUTPUT);

  Serial.begin(9600);
  delay(5000);
  uint32_t t0_m = millis();
  uint32_t t0_u = micros();

  Serial.print(micros() - t0_u);  // Relative time 0.
  Serial.print(", ");
  Serial.println(millis() - t0_m);  // Relative time 0.
    digitalWrite(D4, HIGH);
    delayMicroseconds(5000);
    digitalWrite(D4, LOW);

  Serial.print(micros() - t0_u);  // Relative time 5000.
  Serial.print(", ");
  Serial.println(millis() - t0_m);  // Relative time 5000.
    __disable_irq();
    digitalWrite(D4, HIGH);
    delayMicroseconds(5000);
    digitalWrite(D4, LOW);
    __enable_irq();

  Serial.print(micros() - t0_u);  // Relative time 10000.
  Serial.print(", ");
  Serial.println(millis() - t0_m);  // Relative time 10000.
    digitalWrite(D4, HIGH);
    delayMicroseconds(5000);
    digitalWrite(D4, LOW);

  Serial.print(micros() - t0_u);  // Relative time 15000.
  Serial.print(", ");
  Serial.println(millis() - t0_m);  // Relative time 15000.
}