nope wouldn’t help in the slightest.
If he has heard a song before without even remembering it, and then when writing a song recalls it while thinking honestly it is something new, then this wouldn’t help.
There have been songwriters who borrow
parts of songs and get away with it. Other cases are worthy of court cases and suing.
Borrowing:
Beatles —Birthday
from: Just a Little Bit, Roscoe Gordon
Beatles—All You Need is Love
from Chanson d’Amour, Fontaine sisters
(the da, da, da, da, da after all you need is love)
Rod Stewart, Killing of Georgie, “oh Georgie stay” part
From: Don’t Let Me Down, Beatles
Lennon: “The lawyers were asleep on that one”