I think what they meant was G4 coated in adv Ryou and ACoC.
So basically at this point base Luffy's form in some sence is stronger then any gear.
But this is true for some time period he will be able to use ryu in G4...but it will cost him too much
But at some point Luffy will need the physical power of Gear Fourth or a similar mechanism, he can't rely on haki forever; that'd be like expecting Kaido to not perform physically stronger techniques (such as Ragnarok compared to Thunder bagua) just because both can be applied haki. Base Luffy shouldn't be stronger than in Gear Fourth.