Apple's USB-C to SD card reader (USB 2.0) adapter is compatible with the iPhone 15 Pro, which has a USB-C port for direct connection of external USB-C devices. To transfer photos from an SD card, simply connect the adapter to the iPhone 15 Pro via its USB-C port, then insert the SD card into the adapter. No additional accessories are required to transfer photos from a standard SD card.
However, it's important to note that this adapter supports USB 2.0, so transfer speeds will be slower compared with a USB 3.0 adapter. Also, the SD card must be a standard SD card; if you have a mini SD card, you'll need a mini SD to standard SD card adapter to insert it into this reader.
In a nutshell:
- Plug the USB-C to SD card reader adapter directly into the iPhone 15 Pro.
- Insert the SD card (with an adapter if it's a mini SD).
- The iPhone will automatically detect the photos and import them.
- No additional hardware required.
I think you misunderstand or confuse Roman numerals with Arabic numerals:
UHS-I and UHS-II vs. UHS-1 and UHS-3
The symbols used for the UHS speed classes are easy to misunderstand: While UHS-I and UHS-II refer to the bus speed, i.e. guarantee that the corresponding products achieve a data transfer between memory card and device of 104 (UHS-I) or 312 MByte/s (UHS-II), the labels UHS-1 and UHS-3 indicate the minimum speed at which data can be written from the device to the memory card: 10 and 30 MByte/s, respectively.
The following applies: Devices that support UHS-1 or UHS-3 also support UHS-I or UHS-II.
Unfortunately, we cannot answer this question because we have not been able to try it out in such a form. However, I'll put the question in the community, maybe a user can help you :-)