I think it's because helium neon lasers were among the first lasers, and it was the first "yellow" to be found. But diffusing it into something, it is definitely orange. I frequently show it to people and use it in presentations and they usually comment on it being orange far more than being yellow.
Color is subjective anyhow, everyone sees differently, and when putting two wavelengths side by side, their appearances change as the eye now has new queues to give it a frame of reference, the light is so intense compared to background lighting your eye is overwhelmed from the extreme stimulation, so it guesses at the color in a sense. But by introducing another at the same intensity, it now has a frame of reference to work off of. It's fun to experiment with this with several close WL lasers at similar powers. Like 532, 543.5, and 561 all at 5mW. They look similar on the wall, particularly the 532 & 543, until you put them together, especially with 561. Same in SPADES for red. 632.8 and 650 are red for sure...until you put 670.5, 675, 680, and 690 on the wall too. Now all the sudden, they're orange. 612? Nah. Add 604 and 607... Now 611.9 looks even more red orange.
Now do the same under fluorescent lighting vs. natural light...The eyes are subjective and easy to fool. (One reason I do my spectral stuff in the dark
)
On a separate note....
Sit in a white room with only a powerful green laser on for a few minutes (not staring at the dot, just letting the diffuse light illuminate the room), then turn on the lights and everything looks pink, as it takes time for your eye to recover from the intense green only stimuli (leaving only red un stimulated) so everything in your vision is red shifted for example, until the eye recovers. Do it with all the primaries, & this doesn't happen. Both for similar references as mentioned above, and because of some biology factors I won't delve into here.
