I think u r correct. Sigmoid is just a function, it is an element-wise operation thus does not have a specific input shape.
layer = nn.Linear(INPUT_SIZE, OUTPUT_SIZE)
sig = nn.Sigmoid()
inp  = tc.randn(BATCH_SIZE, INPUT_SIZE)
inp = layer(inp)
inp = sig(inp)
print(inp.shape) # (BATCH_SIZE, OUTPUT_SIZE)