Watson filmed Malcolm Pointon's last semi-conscious moments before he slipped into a coma in Malcolm and Barbara: Love's Farewell.
In an interview with BBC Radio Five Live, Barbara Pointon said: 'The film ends with a freeze frame, a still image which very simply, sensitively and poignantly.
'It sends the message Malcolm has died. Does it really matter if it [the death] was two minutes, two days or two weeks later.The message was that Alzheimer's kills.'
Filmmaker Watson apologised to Pointon on Five Live about the furore, which arose because journalists were given the impression that viewers would actually witness the death of Malcolm Pointon. 'I'm so, so sorry,' he said.
'I'm not a greasy pole TV climber, I make real documentary films, about real people and I live in a real world.'
Watson was asked by Five Live presenter Victoria Derbyshire 'Did you say [to ITV] 'I'm going to film a man dying?'' Watson replied: 'I didn't describe it. I just showed them the film.'
He went on to say that the whole situation had been 'misjudged'.
'The [ITV] press release uses phrases I would never use, I don't talk about 'passing away'. People die,' he said.
Watson added: 'My guilt is that I didn't see the press release or I didn't see it properly. Today the assumption is absolutely that I have read it, I don't believe I have, I did not write it and I certainly did not come to the press and say I've filmed a man's moment of death.'