Sort of... In an interview I read, Sam Smith admitted that most of his songs are born out of a collaboration between him, a musician and a lyricist.
The three of them will sit down and write music together.
This might seem a little strange, but it's actually very common within pop music these days.
Some people might be critical, but the reality is that almost all pop music is written in a similar way, regardless of how much input the artist has.
Most artists have entire production teams and musicians behind them, helping them generate their sound, come up with lyrics, concepts, artwork, and more...
Sam Smith is also fairly unique in that he didn't have a musical background to begin with.
His mother was a banker, and his dad stayed at home looking after Sam and his sisters, so musical inspiration seems to have come from within Sam himself, rather than an external influence.