Well I have both PW1 & PW3. My PW1 is still on fw 5.4.4 , but I wasn't lazy to unpack the fw 5.6.1.1 update bin and confirm that cramfs img doesn't contain Bookerly ttf files.
Speaking of that cramfs file: how difficult it would be (for Windows user / Linux beginner) to replace original Bookerly ttf files with version edited to change line-height (=reduced WinAscent), recreate the image and replace it using USBNetwork? So mod-ed Bookerly could be used for all book formats (mobi, azw3 and kfx), since IIRC fonts hack supports only azw3 books.