Well of course they are, one of the very first
developer diaries talks about what they do with music in the game.

While it is still MIDI, it's not the same as those files you have there. Jagex has compiled their own sounds together, and have added extra sounds that are not in traditional MIDI sounds.
Because of the many different implementations of MIDI music stock sounds, it can sound different depending on your sound card, operating system, etc. This is where Jagex's MIDI music is different, they actually have you download all the sound files as well as the information on what sounds to play when.
Those MIDI files you have are likely before the update to Jagex's sound bank, or are fan compiled to sound like the current music. They wont sound exactly the same as the current in game music.