I just learned that what AMEX calls "cash back" is a balance that is set aside for up to 12 months and is only credited to your balance every September without generating any returns. In the meantime, if I have any balance on my credit card, AMEX charges me 20% APR. That means that the actual cash back that I get is effectively less than advertised.

I guess that this is technically legal because the policy is specified in the small print footnote:

Cash back is applied as a credit to your account annually and will appear on the statement issued in September of each year.

But it still feels very shady and it borderlines misleading advertisement. It feels like AMEX is trying to exploit the lack of financial education of the general population.

Once you take this into account, the cash back on AMEX cards is much worse than other banks that let you use the cash back every month. Given that lots of vendors don't accept AMEX, I am thinking of canceling my AMEX on September and switching to a different bank.

Are there any advantages of AMEX cash back cards relative to other banks?

Edit: some people commented that is how every cashback card works. That is not true. My wife's cash back card lets her credit the cashback every month instead of once a year. The same was true about every credit card I had in Mexico and the US before moving to Canada. By paying once a year, AMEX is essentially giving its customers 20% less cashback than advertised.