I haven’t actually seen reasoning for Sage being more intangible than CS ghosts, so rn it’s just Sage being relative to them
Coulda' sworn there was something on the topic a few pages back.
If that's the case, it's only 2 layers, no?
Boos can phase through walls & other stuff, IIRC, even when not using their Intangibility, & other characters can harm Boos, so that's 1 layer.
When they do go "invisible", most things other than Superguards (In TTYD.) & the Star Beam can't affect them, so that's a 2nd layer.
Same for Magikoopa-granted Intangibility, IIRC, as shown by Duplighosts (Which copy other physical attributes, like being electric or explosive.) copying Lady Bow & then being turned Intangible by a Gray Magikoopa being able to be made tangible again via the Star Beam.
Star Rod MIGHT be able to undo it, but the Star Beam is done by the Star Spirits who created/oversaw the Star Rod, & the Star Rod has an anti-feat of being unable to hit Mario & Lady Bow when Bow uses Outta Sight.
This limitation could be Game Mechanics, though; The only instances of breaking Intangibility, other than the Star Beam, which has plot-related reasons for removing buffs, are all player-favoring, in a game that heavily favors the player. (Like player's side always getting the 1st turn, for example.)
& Repel Gel offers the same Intangibility that the Star Rod, which can grant wishes & grant Bowser Invulnerability the Star Beam can't negate until it's upgraded to the Peach Beam.
(Though, it can negate base Bowser's Star Rod Invulnerability; It's after she uses the power up machine arena thingy that the Invulnerability becomes too much for the Star Beam to negate.)
So it could just be devs wanted player-favoring Invulnerable Intangibility, & game mechanics were made in service to that, & the Star Rod SHOULD be able to Negate 2-layer Intangibility, since it can grant Invulnerability that can't be negated by something that CAN Negate 2-layer Intangibility.
Plus, the Star Rod's wave attack is able to negate every other buff, IIRC, like Charged Status, Petrification (Maybe?), Cloud Nine & Water Block, so it's a little weird this wish-granting thing would only be stopped by an "Invisible"/Intangible status, when its creators (The Star Spirits.) can get around that. (Against Bowser's Star Rod without his power-up machine, anyway.)
I'm unsure. What do you all think?