That is my recollection as well. Also I remember Psycho Mantis would make some comments about the content of your memory card before the fight.
Another favorite of mine is The End in MGS3: Snake Eater, he is a sniper hiding in the woods and it takes like an hour of game time to beat him down. I seem to recall if you save during the fight and change the date forward a few years on your PS3, when you reload he has died of old age waiting for you to come back.
I thought I read elsewhere there were some GPL 2 parts in there too, I guess not.
I tried to find a source for this more credible than “I remember reading it on Lemmy” but couldn’t, now that the repo is deleted nobody can confirm. Perhaps some forks still exist… 🤔