It can, yes.
A solid repeatable signal at a shallower depth may not ring up the same at all depending on conditions, soil, angle of the swing, item placement in the ground, etc. Coil configuration (size, shape) may change signals as well. It's a game of guesses really. But give yourself the advantage and dig based on tones.
edit: i generally dig based on tone, and i have noticed that a lot of pennies ring in as dimes on the VDI. That's a good example, and dimes/quarters can be mixed as well. So the VDI doesn't accurately display what it is 100% of the time, but it gives you a general reading