Indeed, I did a ton of testing that's why I can confidently say it is guaranteed. And for the displaying, the only thing that stops me is the players not playing once it hits 99% and waiting for it to go down so no one would play anymore in some games. The concept is the RTP goes down than up (of course random factors intervene so it won't be a uniform process but it eventually goes back to 99%). Thank you for your remarks and I will be working more on transparency. If you have a suggestion about it, it would really help a lot because I'm finding difficulties to introduce more transparency without ruining the games.
As long as the algorithm is built around independent event "theory" -- previous results won't affect next results, past RTP doesn't affect future RTP, displaying RTP won't matter much I think. It's pure superstition since RTP swings wildly, and don't forget that
slots in the hot state produce more than 100% RTP, so 99% isn't a benchmark. You can display weekly, monthly, and all-time RTP. We will expect weekly or even monthly RTP swings wildly depending on the volatility setting, and all-time RTP will be close to 99%.
But if you try to build an algorithm that takes into account previous losses, when the probability of winning increases after a long losing streak, displaying statistics is a bad idea. I heard this kind of slots exist, but I never get to play one.