These leapers have some merit in combination with less awkward pieces.
Ralph Betza's 'Half-Duck' combines (0,3) and (0,2) leapers with a (1,1)
Ferz. This piece is called the 'Lion' in Greg Strong's Opulent Chess
and a couple of my variants. Back in the previous century I invented the
'Unicorn', which can [1] move like a Knight or [2] move like a Knight to
an empty square and continue with another Knight leap to a location three
squares away diagonally. Thus it's move includes a (3,3) leaper WHICH
CAN BE BLOCKED. Replacing Knights with Unicorns in FIDE chess yields the
following Fool's Mate: 1.Uc3 c5? 2. Ub4 mate! (Black cannot block both
c7 and d6). Later on I decided to use the name Unicorn for another piece.