You are still appending to the global list, so the list will grow in each forward pass.
To store only the activation of the last forward pass you would need to reinitialize the list or clear it in any other way:
with torch.no_grad():
    out = model_ft(torch.randn(1, 3, 224, 224))
    print(len(total_feat_out)) # prints 10
    total_feat_out = [] # reinitialize list to delete old activations