You're right. The NY triggers are stronger than the stock trigger springs. However, a Glock WILL STILL FIRE with a broken trigger spring.
During LFI-1 in June with Mas Ayoob, we discussed this exact combination at length. One of the students was an IDPA Master and Glock armorer. As I recall, there was some kind of failure where you could still run the gun with a NY1 trigger spring, but you had to do some other step if the stock spring broke. I may have misunderstood, and I defer to NY27's armorer expertise.
There are two other advantages Mas related to us: the first has been discussed here - the NY1 has a crisper reset than stock, as the stronger spring "assists" the trigger back forward.
The other is legal and some disagree with Mas on this: Glock specifically states the 3.5# trigger bar connector is not for duty or carry, but they do endorse the 3.5# trigger bar/NY1 spring
combination for duty/carry. Mas is concerned that a prosecutor or plaintiff's attorney could try to paint you as reckless or negligent if you were involved in a self-defense shooting and had modified your carry gun counter to the manufacturer's specifications, such as using a 3.5# connector with the stock spring.
Now that Glock endorses the 3.5# connector/NY1 spring combination, Mas calls that "the holy grail", because of its performance benefits without providing ammo for an opposing attorney.