We cannot really conclude this.
As a matter of fact, players from 6ft4 and above are statistically way over-represented in the top 100 compared to players of about 6ft. Height follows more or less a normal distribution in the population, meaning that there are very few people standing, say, 6ft5–6ft6 compared to 6ft in the population at large, so if it was really preferable to be 6ft1 rather than 6ft5–6ft6, then you would also expect them to drastically outnumber the taller men in the top 100. Yet that's not the case. There are far more big men near the top than you would expect from how rare they are in the population in general.
So from that alone, we must conclude that being above 6ft3 must carry some real benefit in terms of becoming a top tennis player.
Yet, as of now we haven't seen this trend carry over into creating tall ATGs or dominant players. It's hard to conclude precisely why that is, and we cannot say for sure that being below 6ft–6ft2 is necessarily the ideal for being an ATG compared to being taller. One thing you have to take into consideration is that to become an ATG, you need a very rare talent. Might just be that this level of talent has occurred more often in players standing 6ft1 than 6ft5 simply because there are far more of them – a matter of likelihood and numbers. Statistically, even more people around 5ft9 should have this level of talent, but at that point the lack of height becomes too much of a limiter.
Then again, it's also possible that being ~6ft6 is a big advantage, but only up to a certain point and not beyond that. That it also carries a certain ceiling on how good you can get, so to speak. It's hard to say for certain as of yet. The game has been moving in a taller direction in general in the last decade, and my hunch is that we'll soon see a dominant player above 6ft3. Zverev and Tsitsipas are obviously big boy candidates.