Last time this one came up, the answer was that NO NDB in the UK needs a BFO.
But if it did, the answer would be with the way the ident is generated. If it is AM (in which case the carrier is constantly transmitted) then a BFO is not needed. A BFO is needed only if there is no modulation and the carrier itself is being turned on/off with the morse code.
It is possible this is a fossil in the ATPL syllabus...