this is not a bug, the process require careful attention.
i’ll outline the high level concept of the process to change ETH to BNT as described in the post.
step 3: in this step, access the EtherToken contract
step 4: here, you permit the BancorChanger (this is not the BNT token contract) to access your EtherToken contract
step 5: now you access the BancorChanger contract (the actions found in the contract include the “change” which is required for changing ETH to BNT)
step 6: this is where you actually change ETH to BNT. the changer access your EtherToken contract, takes the amount you indicate and change it into BNT (using BNT token contract)
if the process is still not clear, please let me know