I had rim brakes on the front. I removed them. I put a disc brake on the front. The rotor is fitted to the left side of the wheel. According to your thought process changing from rim brakes to disc brakes means one should tighthen the spokes on the rotor side.
Well, you can't just willy nilly change a rim brake wheel to a disc brake wheel. You have to change the hub to a disc brake one with an offset on the left. You make it sound like it is just a matter of changing the brake, when it is in fact a new hub, new fork and new brake mechanism that is involved. But yes, on the latter wheel, the spoke tension on the left will have to be higher than that on the right.