4.65% is the total of the prize fund.
There's no way most will achieve that rate because the high value winners are receiving much more than 4.65%, so there has to be many winning less to make the prize total add up to 4.65% of the total funds invested.
However, they are tax free, so even a lower rate can be a good one.
For example, my son.is a higher rate taxpayer, has maxed out his tax free ISA and used his £500.tax free interest allowance. That makes his winnings of 3.5 percent worth to him 5.83% which for instant access is good and he also has the fun each month.
But, many people are in a different position, paying tax at other rates, so.its definitely a personal decision.