It’s very configurable. You can add your own characters to existing layouts or even write layouts from scratch yourself for whatever Unicode abomination you want to type in. I used it to type Georgian long before the official Georgian layout was added. Pretty cool stuff.

Nah, not really, þ was used for both sounds throughout the history. Reviving this thing would make sense with a letter eth (ð), assigning one sound for each, as in “wið/boþ”, which is easier to read for language learners. But the person above clearly just wants to be fancy.