Try looking in UK specifically, or scroll down that list you got. Typing 'farthing' gets you quarter farthings and third farthings, but no farthings from Victoria onwards. And nothing if you search for '1 farthing'.
Who's going to use '¼ penny'? I figured it out, but the coin says 'farthing' on it. It's 1 Farthing. No one looking for American pennies types in '1/100 Dollar'.
You're reporting a "bug." It's not a bug. It's functioning correctly by returning coins with "farthing" in the face value. Since 1 farthings are entered as 1/4 penny for face value, they're excluded in the search. If you want their face value changed to "1 Farthing" you should be posting in the Numista coin catalogue forum with "requesting the modification of a coin in the catalogue" type post or submit a change request for each coin which will go to the referee to validate. Hence, my suggestion to discuss it with the referee.
The really funny thing is this is not a problem on the French site which lists the face value as, "1 farthing = 1/4 penny = 1/48 shilling = 1/960 livre (1/960)."