There is truth in the claim of price volatility scaring away certain merchants, but I believe as the industry matures mechanisms will be in place for quick conversion to fiat so that merchants are not hit with the risks. Also, given that this criticism is coming from a centralized entity with a reputation of high fees, we should be skeptical of these comments.
there is no truth to that actually.
you can easily verify this by looking at the growth of the number of merchants that have started accepting bitcoin over the past years and also the total amount of bitcoin that has changed hand among merchants and customers during that time. you can clearly see that there has been a big growth in both which shows that it is not "scaring anybody away" it is just happening slowly because bitcoin adoption is happening slowly.
I agree with you that merchant adoption is growing, especially with the Lightning Network, but that does not contradict what I wrote. Bitcoin's volatility is a concern for some merchants, and insofar as it is, it will play a role in bitcoin's rate of adoption. However, I believe over time the bitcoin price will stabilize.