@fermon
I don't think you understand the purpose of Kernels converted to FTF files. First of all Unlocking the Bootloader on any phone isn't exactlly the ability to use Fast Boot Mode but the ability to flash Unofficial Kernels(Custom Kernels),independently of being it done either with Fast Boot Mode or Flash Mode. So by Unlocking the Bootloader of a Xperia Play(Using the Test Point Method) with "Bootloader Unlock Allowed: No" you get the ability to Flash Unofficial Kernels(Custom Kernel) but not the ability to use Fast Boot Mode, and so the need of Flashing a Custom Kernel via another method arises and that's where Converting Kernels into FTF files and Flashing them via Flash Mode comes into place.
Now, I am not a Developer nor an Expert in hardware, but in theory this method should at list work on all 2011 Xperia Phones. If you would be willing to try this on your Xperia Mini Pro and it ended up working. This could help a lot of people(with "Bootloader Unlock Allowed: No") not only the Xperia Mini Pro but all the 2011 Xperia Phones.
So if you want to help, try Unlocking your Bootloader using the Test Point Method. I also want to say that this could be risky since it only has been tested on the Xperia Play.