Apple's quality processes have been fiercely criticized for a while, the company chaining various problems, especially software. The latest example is the SoC case, whose frequency drops to match the wear of the lithium-ion battery.
So much so according to Axios that Apple has decided to postpone some features of iOS 12 to focus on performance and reliability. In this way, a 2019 revision of the welcome screen and some native applications (notably Mail), improvements to the taking and editing of photos, or sharing will be rejected.
This is obviously a rumor, but it has the merit of being aligned with the events of recent years, 9to5Mac having had the same echoes. The explanation given for the battery, even if it is valid, has nonetheless illuminated two problems: a serious lack of communication, and an increasingly negative perception by the public of the impact of the updates.
Apple has every interest in avoiding a situation of mistrust, which has been apparent for some time. 65% of iOS device users are currently on the 11.x branch. A much slower evolution than in previous years. To release an iOS 12 which would be presented as faster and more stable would thus be the preferred solution.
Confirmation (or not) probably next June, at the next WWDC.