oh my god, you're right, they just used an f, no wonder I found it so bad! That is really annoying. Enraging even.
I should have noticed, it has a full cross bar, I guess it's my fading eyesight and also the white text of green is perhaps not the best contrast.
The text doesn't use an `f`. If you copy from e.g. the 1700 passage you get `ſ` not `f`.