There’s a lot of ways to work with the mnemonics. WK’s is just a suggestion that works for a lot of people, but you don’t have to use it. There are some flaws with it. Whether they’re a problem or not, though, is up to you.
You already mentioned accent. Non-US English speakers often have to adapt the mnemonics based upon their pronunciations frequently.
Another thing which you’ve probably not quite hit yet (but soon, within the first 10 levels) is WK sometimes uses the same mnemonic device for different sounds at different times. It can be quite frustrating if you’re not prepared for it.
Some people (like myself) use our own systems. You can see a thread on the system I’ve been using here. That links to a few other discussions on the topic. Also do a search for “Consistent Mnemonics”. You’ll find a lot of different approaches that different people have come up with over the years. You might have to experiment a bit to find the one that works best for you.