[wolfi008]

We should not forget that different people have different talents. That creative superstar guy may have been great at coming up with new stuff but terrible at maintaining stuff. Or at debugging some urgent prod issue under time stress on a saturday evening. You need those people too that enjoy the day-to-day maintenance to keep the house clean, or the occasional firefighting. A good team contains all those types and they complement each other.

[Nevermark]

In this case, they were great maintaining stuff too. They remained available to dip into that work whenever it helped.

But as a rule, it would not have been challenging enough to keep them engaged for long. And it would have been a waste of their talents for themselves and the organization.

It wouldn't just have wasted their time directly, but wasted the opportunity for less (but still A-grade) developers from diving into a new area and maximizing its value. There was still lots of creative work to be done. These were not trivial new areas.