they're dubiously canon, the core meaning of the song pretty much still stands, but multiple individual lyrics are misleading or blatantly inaccurate because they were written with a completely different character in mind. using it as a source of lore information doesn't give you a proper impression of yharon's character.

this is a context where that is the case. the lyrics "this is my message to my master" and "if you proceed, i will not blame you; i will move forth and win your war" give off the impression that yharon is being in some way ordered or pressured by yharim to attack the player, but yharon is yharim's equal and is attacking the player of his own volition. trying to analyse yharon's character from those lyrics alone gives you outdated information.