What were ATC doing trying to give separation for VFR traffic in class G airspace*? If you were told not below 2000' for the calibrator, then ATC are giving you separation. However separation is not required for VFR from IFR except in class C, B or A airspace (SVFR in class A of course). So why were you restricted to not below 2000 feet?
There are reasons for the flight rules in various classes of airspace. This shows one of those reasons.
*OK, could be class D zone, but still applies. In class D only IFR from IFR separation is required.