I like the idea of saving HBD throughout 2024, at least partially.
Regarding the APR, it's true it's paid every 30 days, but you add HBD every week, and the APR applies to a different amount every week. A better way to calculate it would be weekly, after every deposit, in my opinion. Unfortunately, it would come lower than your amount, but 20% is 20%, for whatever time it will still be available.
For example, after week 1, the formula would be:
20 * 1$ / 52 / 100 = apr1
After week 2:
20 * 2$ / 52 / 100 = apr2
and so on.
Every 4 weeks or so you add the sums or the previous 4 aprs, after the interest would be paid.
I hope it makes sense.