if it works for you greattry it before knocking it.
things and recommendations always change. Like open bridge has become more popular these days. Even the post here on Hoppe instructional.
Bottom line you have to find what works for you and not what some instructor say, experiment.
For me, gripping like that makes my stroke straighter and I'm more accurate on those long shots on a 9ft with tight pockets. My power draw also works better.
but
not sure you will see many pros like that OR instructors recommending that