If I write a clue that seems relatively obvious I always google it to see if it's been used before, and almost invariably find that it has ('Liking a swan song' for PENCHANT was one I remember recently). So it's almost inevitable that at some point the same clue will appear in different puzzles by different setters on the same day. Having said that, some setters are not averse to 'recycling' their own clues, so these two puzzles could have the same author, thus substantially reducing the level of coincidence.