Here's the official line on the processor:
The iPad mini 2021 uses the A15 Bionic chipset, which is also in the iPhone 13 series. According to Apple, this will include a 40% faster CPU and an 80% faster GPU than previous iterations of the device.
The clear variation between the A14 and A15 is in graphics processing: While the A15 processor in the iPhone 13 has four GPU cores, just like the A14, the A15 processor used in the iPhone 13 Pro and the new iPad mini has five GPU cores.
Basically the same is a little misleading in some aspects, and the title is a bit of clickbait. Better GPU is an important difference in driving the iPad Mini screen.