Regarding this, this minimal reduction is not going to change anything in the long term results, because House Edge will continue to be a loser, and in the short term, well, having 0.5% more in his favor will make him have some more positive sessions and will last a little longer, but I don't think he is going to notice it much either.
If he is looking to “make money” playing slots by reducing HE he is taking the wrong approach.
Considering that I play long-term, it means a lot to me if I have, for example, an RTP of 99.30% instead of 99% and on a large number of hands it makes a significant difference, at least for me. My strategy is based on RTP, I try to "artificially" slightly increase RTP, so everything is important to me. I'm not looking for the holy grail and a winning system. I know how RTP or house edge works in the long term.
So, if you know how it works, what are you expecting? Lose money anyway? Because the House Edge means you're going to lose money, even if it's a little less. And the most common way you can reduce it (or increase your RTP if you prefer) is to bet a lot. So, you bet a lot of money and the house offers you an RTP of 99.3% instead of 99% (via a VIP program or bonuses or whatever.), which was the one you had originally, but that's because even though they take less commission percentage-wise they will probably make more money with what you bet more.