I agree with you on this. And the text used the word "like a lion", and by that it doesn't meant that the lion is the devil, it is more like using the lion to describe how the devil tends to behave. Therefore it is not enough evidence to truly associate the lion as the devil.
Coming from a former commonwealth country, growing not knowing much about the monarch, other than what I have learned in history class.
This topic does gives me a very good insights into how people from the commonwealth and non commonwealth view the British monarchy.