MFI certification I don’t. They didn’t do it with iPads or MacBooks, why with iPhones?
Kinda already answering your own question. Those products converted to USB C a while ago, and there hasn’t been a technical reason to not convert iPhone for at least as long. Why not iPhone? It’s probably because if I had to guess, the MFI business is like, a lot of money. Probably hundreds of millions.
If you follow apple and the rumors fairly closely, this is one that at this point will be a surprise if it doesn’t happen.