Yes, he was creating -- just for not always with the Beach Boys in mind, first and foremost, which is why a lot of that stuff went unheard at the time, or eventually crept out, with a few tweaks, as you describe with Sail On, Sailor. Interesting info, too, about the lyrics -- I always wondered there were so many names on it, but from what you describe, I suspect it's the "change a word, get a third" phenomenon that often happens with these thingsOne of the most interesting things I picked up from the discussion was what Brian's involvement was from roughly 1969 through 1973. He was often out of it (mental illness and drugs) - but he was also working on a regular basis. It wasn't like he just dropped out. He worked when he wanted to work. Sure, he had a hard time finishing songs up - but he was still creating. Sail On, Sailor was one of those songs.
I'm also surprised you didn't mention A World Of Peace Must Come, an album recorded with poet Stephen Kalinich -- which Light In The Attic finally released in 2008. That was another project that took up a fair amount of Brian's time, to the annoyance of the BBs family and franchise, who wanted his creativity harnessed for their benefit (ka-ching, ka-ching). Or so I've read. Anyway, the '69-'73 era is probably my personal favorite one of the band, which (to my ears) resulted in some of their richest, most complex and creative music.