Runelite feature is still pretty buggy for most people, BUT...
Basicly using osbot injection client or the runelite client is exactly the same.
The are both 3rd party clients that use injection and that's all jagex can see.
Mirror is intented to work with the original client, so jagex can see you just their client and not some 3rd party client.
So using runelite would probably be the same as using injection. (Since runelite is basicly that)
It was added recently bcs it was requested a lot...
No idea why it was added eventually though.
Exactly ^