Question Getting Length/Magnitude of particle velocity vector as a float

Hey all! I'm having a really frustrating problem that I don't fully understand.

I have a butterfly particle system that uses vertex displacement to create wing flapping motion. This works great! Now, I'm trying to make the butterflies flap faster/slower based on their velocity.

I've taken particle velocity from my output stream, turned it into a vector3 and am using the Length node (whose documentation SAYS it returns a single float) but I am absolutely not getting a float! I'm getting this value.



If I ADD this value to the particle's color, it works perfectly! Particles that are moving faster are rendered as whiter/brighter than particles that are slower.



However, when I plug in its output as a multiply to alter my time, I get an incredibly strange pattern that causes strange distortion.



The thing is: I KNOW multiplying these nodes by a float (in this case, a public field input float for Flap Speed OR just a flat number) creates the intended behavior I want. So, clearly, Length isn't returning a float! I have no idea what's going on! Or how I could possibly GET a single float value from my velocity vector.

All I need is a float of magnitude, or even an average of the greyscale image that length produces

Please help shader wizards!