<i>I understand the implications and everything</i>

I don't think you do.

<i>I can always say "I forgot[...]" Then what happens? I go to jail for 4 months?</i>

No, you go to jail for a few months and then they take you back to court to see if your memory has improved. If you don't have the key or if you produce a key that doesn't reveal the data they wanted it to, you go back to jail for longer.

If you can't produce the data the state demands, either because it isn't there or never existed, or because you really forgot, then you can stay in jail the rest of your life.

That is the purpose, goal, and implication that so-called law enforcement wished for and got from data investigation rules.