Can this Noise Suppression Filter/ RF Inductor be used in buck/boost converter instead?
Say I have a buck/boost converter operating at 100Mhz.

It's very unlikely you've got a buck/boost operating at 100 MHz, for physical reasons of switching losses and core losses.
As you've noticed, core materials don't work like perfect inductors once frequencies rise.
So, if your inductor has any core material that is frequency-dependent (mostly: anything but air-core) you'll have to make sure it's not lossy at high frequencies. The opposite of what you're looking at.