For this specific gradient, see https://oklch.com/#0.7017,0.3225,328.36,100 and https://oklch.com/#0.86644,0.294827,142.4953,100, and look at the Chroma panel, see how far out of our screen gamuts they are (even tick “Show Rec2020”, which adds a lot of chroma around blue–green and magenta–red), and try to imagine the colours between the lime and magenta (in either direction). The red direction is probably the easier to reason about: there’s just no such colour as a light, bright red. You can have bright or light, but not both. (Its 3D view can also be useful to visualise these things: you’re building a straight-line bridge between two peaks, and there’s a chasm in between.)