According to sources from The Information (via macrumors) Apple had planned a significant advance in the graphics capabilities of the iPhone 14 Pro, but this new graphics processor (GPU) was removed at the last moment due to technical problems, unheard of for constructor.
iPhone 14 Pro, GPU Ray Tracing problem discovered at the last moment
This new GPU notably included Ray Tracing performance, but Apple engineers were said to have been too ambitious, and the prototype used far too much power, impacting battery life and causing overheating. The flaw was discovered quite late in the development cycle, and Apple had to - almost at the last moment - abandon the processor to use a model similar to that found in the chip of the previous iPhone 13.
This event is apparently unprecedented in iPhone history, and explains why the improvements in graphics performance of the iPhone 14 Pro are only marginal compared to the leaps of previous generations.
