Of course. So it would not be illogical to assume that one could see some niobium inside that adit.
Just as concentrations of gold, silver, copper or other elements could be seen inside a concentration of ore in some areas whereas it might not be visible (but present) in other areas.
Now the pics of the adit are only interesting to me in the sense that it makes it easy to see with one's eyes, the geological formations one encounters as one proceeds into the depth of the adit. Obviously, one would need to get the samples from the adit assayed to know exactly the concentrations of niobium, tantalum etc. But I would assume a professional would know what he was seeing, in particular.
and yes, concentrations of elemental anything can vary across any distance...even an inch.