For those unaware, this comment is referring to premium bonds in the UK[1]. It is a very interesting system, I agree! But there are quite a few parts of the system that make it way more fair than a lottery.
Most obviously, it doesn't cost to enter. So the most you can "lose" is a missed interest income from putting the money in another source.
After that, it's definitely the fact that the algorithm is designed to both pay a certain percentage of people and always have specific return. [1]
You are also limited to how much you can enter to 50k.
With all that in mind, at the end of the day it feels like many small wins over time, with the super random chance of occasionally having a big-ish payout.
It's definitely designed to feel like a lottery, but in reality is way more akin to normal savings than a lottery.
In New Zealand this scheme was called "Bonus Bonds" and was wound up on 26 February 2024. Interest was charged on "wins" just like any other income. Apparently the average return was a paltry 1.5%.