Oscillator

[ivconic]

That would depend on the method of detection, would't it? If it's based on variations of amplitude then high Q offers more sensitivity and therefore more depth.

Regarding reverse Vbe why woul anyone go for it when you can do the same without and with a simpler circuit goes beyond me.

In previous two larger posts i tried to explain and to describe precise context.
So we'll stay within the given context when talk about the details.
One thing is to observe the signal (and test the detector) through the clean air and in lab conditions and quite another if you try to do the same in given context.
Both; amplitude variations and phase shift will be significantly affected by the type and nature of surrounding "media" (soil).
What we have here to deal with is the tough problematic way over the amplitude behavior domain.
Generally; yes: it would depend on the method of detection.