If the Vanquish only has 3 frequencies then I would say it's no great loss for its intended purposes. They're not marketing it as a beach or small gold machine. Blends of 10,15,20 along with appropriate preset recovery speeds, descrimination patterns and iron biases, cover the model's coin, relic and jewelry modes.
Besides, I've never seen anything that proves the Equinox is always blending different mixes of ALL five of the frequencies in EVERY hunt mode. Maybe Park and Beach don't use 40 kHz frequency at all, for example. Maybe gold mode doesn't use 5 and 10 kHz. That's pretty likely.
You just can't tell without picking the software apart. The detector is likely sending all frequencies the same in every mode and the post processing is what does the balancing. So, you could use equipment to test what frequencies are being sent from the transmitting side of the coil, and that would prove which frequencies are present, but it wouldn't prove how they frequencies are processed.