Mark Gurman, Bloomberg:

Software chief Craig Federighi and lieutenants including Stacey Lysik announced the changes at a recent internal “kickoff” meeting with the company’s software developers. The new approach calls for Apple’s development teams to ensure that test versions, known as “daily builds,” of future software updates disable unfinished or buggy features by default. Testers will then have the option to selectively enable those features, via a new internal process and settings menu dubbed Flags, allowing them to isolate the impact of each individual addition on the system.

And:

Prior to iOS 14’s development, some teams would add features every day that weren’t fully tested, while other teams would contribute changes weekly. “Daily builds were like a recipe with lots of cooks adding ingredients,” a person with knowledge of the process said.

Test software got so crammed with changes at different stages of development that the devices often became difficult to use. Because of this, some “testers would go days without a livable build, so they wouldn’t really have a handle on what’s working and not working,” the person said.

The proof will be in the pudding which, in this case, is iOS 14.