its probably a glitch with 3x3s using big cube notation
like Rw=x on a 2x2
but this feels different and something unusual to witness, this does look cool tho
If you want to write babyface algs, that's up to you.
But to actually answer the question: It's not intentional, but it's been in `twisty.js` since the original code from a hackathon in 2011. It happens for exactly the reason you would think, which is that e.g. the stickers on the L face are treated as a 4th layer counting from R.
alg.cubing.net development is frozen in favor of Twizzle, so I'm not fixing anything unless a serious bug comes up. Since this only happens when you use use moves like `4R` (which are otherwise not valid), it's more of an easter egg at this point.