We've gone through several iterations of purple and possible interpretations of Purple on the wiki and recently we've kept it as just another powerful attack. I think we should reanalyze what Purple is.
Something that's been discussed among the JJK community is the
translation for Gojo's Imaginary Mass and Yuki's Virtual Mass, we are shown that yes, the two are the same in Japanese so we should go with how its in Japanese. The theoretical concept "Imaginary Mass" should be dropped entirely as Gege isn't referring to it, nor does Purple really act like it. Instead let's frame Purple how Gege
likely wanted it to be.
Virtual Mass
Virtual Mass can be described as "added mass", not added mass in the sense that a rock is added or a mountain or some object, it's mass that is dependent on everything Purple may interact with in its way, accelerating it (the object not Purple). This is why when we see Purple fired, it doesn't erase or annihilate matter like so many believe, it instead sends everything flying as its pushing all the other stuff out of its way to occupy the space. For reference we can see it sending things flying out of its way;
1,
2. Though one instance where many would believe its erasing matter, the Toji
example, what's happening is Purple is accelerating the air and part of Toji's body so fast that it gouges right through Toji and beyond him, destroying everything in a cylindrical shape as Purple is a sphere itself. And we can look at the wording to hopefully help recontextualize Purple; "
an imaginary mass rushes forth", Purple is not this imaginary (virtual) mass, Purple is the catalyst for it, what's rushing forth is the "added mass". I didn't really understand for a bit and I probably still don't lol, but this
video should show you in a easier way what Purple is roughly doing, although at a much lesser extent. To put into Purple's context, imagine the board as Toji and the water as air, Purple is the chopstick accelerating Toji and the water to push it out of its way. And against Sukuna, at a higher extent, we start to see its limit or at least resistance; like with the smaller board (in video) Purple can't shoot through the building as easy as it did against Toji as the board (building) isn't big enough for the 200% Purple to poke straight through.
"But what about Yuki?" She's doing the same thing, she's imbued herself and Garuda with the very physics of Virtual Mass. This is why she's able to hit so hard and why Ganesha can't target her, because her effective mass is too great in a semantical and pragmatical sense to be contained. This also doesn't necessarily speak to how much effective mass Yuki has as we don't know the limit of Ganesha's ability.