Polish - 'kto' versus 'kogo'

I found most explanations on when to use 'kto' and when to use 'kogo' don't seem to make much sense when you actually see these two words in practice

Now if you are at the absolute basic level you use "kto" to mean "who" in the nominative (basic statement) case and "kogo" to mean "who" in the genitive (after the verb) case. If you don't know your cases yet see my Which Case? page.

So then the kind of example given is usually something like:

• If you are asking a super simple question like "Who is this?" then it's "kto" - "Kto to jest?"
• If it's more complex like "Who do you love?" - i.e. it contains a verb (like to love) - then it's "kogo" - "Kogo kochasz?"

But this doesn't really work because "Who knows this boy?" is "Kto zna tego chłopca?" even though it contains a verb (to know).

The 'Adam' test

A more reliable system is to take the English version and ask "Can I replace 'Who' with 'Adam' and the sentence will make sense?". If the answer is 'Yes' use "Kto".

So:

• "Who knows this boy?" -> "Adam knows this boy?". Makes sense so use "Kto" - "Kto zna tego chłopca?"
• "Who do you love?" -> "Adam do you love?". Doesn't make sense so use "Kogo" - "Kogo kochasz?"