Blaze wrote the vocal parts for those tracks based on music that his band members came up with. Guitarist Steve Wray wrote the main riff in The Brave for example, and all band members except Jeff Singer contributed different parts to Stare at the Sun, according to the At the end of the Day book.
Writing credits:
Born As A Stranger - Bayley, Naylor, Slater.
The Brave - Bayley, Naylor, Slater.
The Launch - Bayley, Naylor, Singer, Wray.
Stare at the Sun - Bayley, Naylor, Slater, Wray.
So they were definitely not written while Blaze was still in Maiden. That Blaze then had some rough ideas for lyrical themes before leaving Maiden, that came to inspire some of those songs, is not the same as them being actual lost Maiden tracks. Blaze also doesn't play any instruments, and therefore can't compose full songs on his own.