I'm saying that when you make a VCO as a "product"
(piece-part, IP chunk, whatever) the expectation is
going to be that it is (linearly) voltage controlled. Not
current, unless you advertise it as a CCO.
So then you would be tasked to take an input voltage
and do what you must, to get a reasonably linear
df/dV across the band of interest. This could be as
simple as a minimal op amp and current mirrors, one
of which drives a I*R feedback leg and another of which
drives the CCO core.