It's doubtful that anyone's perfect, especially when it comes to Spoonerism clues. Azed has previously acknowledged that a weakness of this particular format is that half of the entries have no proper definition, relying rather on the Spoonerised versions and cross-checking.
For example, it seems obvious that the answer to 23 across is DELPHI as only the P is unchecked, however there is no confirmatory definition and the Spoonerised version seems to be DEE FELL ('River dropped') which would give either FEE DELL (consonantal) or DEH FEEL (vocalic) but not DELL FEE where both consonant and vowel sounds are transposed. The preamble makes it quite clear that the Spoonerisms can be either consonantal or vocalic, but not both. Perhaps Azed intended the clue to start 'Dropped river' giving FELL DEE which can be Spoonerised to DELL FEE ?