As Huwyt_Nashi052 said, IR controllers are generally very flexible and allow for receiving/sending arbitrary low-to-medium frequency signals. BL602 is no exception with the software mode the controller provides, giving you access to raw pulse lengths; for example I use it as a pulse frequency counter to interpret a BLDC driver's "speedometer" line, and there are countless other applications like controlling an eInk display's common anode/cathode line.

I must have missed it in the article but a hardware peripheral for interfacing with IR remotes is common in microcontrollers and can be very versatile with the right configuration. It's often used for driving addressable RGB LEDs, for example.

I don't think the article talked about it directly, but there was a block right in the middle of the memory map for it.

Lots of SoCs start by licensing (or already having) an existing MCU or CPU core and adding a bunch more peripherals. They didn't need the die area, so they left the IR peripheral in.

Could also be that they figured somebody might want to make an IR to wifi bridge solution. Or maybe somebody might make some RGB light strip with both local IR control and app control via wifi or bluetooth? It does make sense and IR receiver is a very simple peripheral.