Direct answer, yes, that is possible. But let's think about it, should a 'reputable' company go beyond that action to maximize business profits? I suggest not to stress about it. RTP is something gamblers can't even feel. Just go with the flow on why you gamble.

Let's face it. Do most online gamblers, especially slot enthusiasts, really care about online RTP? Maybe yes at some point but not to the point that we will end up investigating if there's a flaw, especially if we talk about games on a reputable casino. That's why they are called "reputable" in the first place, we can expect that everything is fair. Of course, it doesn't mean that we should be blind about it, but the main criterion now is popularity. A certain slot game won't be popular in the first place if it's trash and full of flaws.

Game providers won't ruin their business by tweaking the original RTP. I can say the same thing about those games provided by the online casino itself. It's hard to build trust in the current vast industry of online gambling.

To simply make this short, stick with reputable casinos, as we can expect that their games, and games by their providers, always follow the original algorithm designed for them, and that includes the RTPs.