While the battery does have the ability to change mode quickly,...

While the battery does have the ability to change mode quickly, the article is rather gushing in praise without real substance.
Did it avert a cascading failure or blackout? As the article states, No.
In reality all the connected generators on the network with spare capacity took up the load instantly - the "shock" causing the frequency drop. That is why they have "spinning reserves" that should be at least equal to the largest generator in case it trips. The fact of a frequency drops for a short time is rather immaterial - it will vary slightly as loads change during any day and is adjusted for. The implication that the "slow" coal generators would take minutes to "put their socks on" is just hype - the minutes would be to bring the frequency back up, not to fill the shortfall of power (else there would have been a 553MW unmatched demand and blackouts).

If it does prevent blackouts or failures that is excellent, probably (as some suggest) it is moderating extreme price points that is a major benefit.