A slow, heavy spin loop is an excellent control option that if place extreme shallow or deep will give you a good ball back to go ballistic smash, but the OP is talking about a fast loop attack.
You normally choose to do this (a slow, spinny loop landing deep) if you need more time to be in position, the ball is low and spinny, or you simply choose control on this shot and look for the next ball to attack strongly. A slow loop is not a bad choice, since if you are good at it, it is very likely to land and give you a better chance next ball.
If the ball is long, has weak spin or is high, a fast loop is a good high percentage choice. Such a situation is a good opportunity for a strong attack to end the point. Attacking players should be ready for these chances and do what they can to set them up often.
It is possible his new blade and rubber simply act different than his previous setup and needs to adjust his bat speed, blade angle, and moment of impact. It is also possible his new FH rubber in stock version is unacceptable performance or a bad glue job. So many things are possible, we just as first choice focus on technique in our comments.
I recently built a bat with H3 #19 sponge and was very disappointed with its performance. Truth is, that sponge is flaming hot garbage without tuning. I did not know that at the time I bought it. My next H3 purchase will be commercial NEO version, a reliable rubber with acceptable predictable performance once it breaks in.