While I agree that he sounds like and probably has no idea, the rockwool block route is actually pretty damn good for developing seedling cuttings aside from rootpouches and air pruning.
Here is the thread from the resident expert when it comes to Rockwool planting, and his results are nothing short of impressive.
Figured I would start a different thread. Most growing is outdoors recently except perhaps rooting the cuttings. All these are growing in Stonewool...Either Grodan Mini- Blocks or the Grow Wool loose media. I will update the thread with all the various hydro techniques as usual. Currently...
www.bonsainut.com
Here is a pic of the seedlings kabudachi I bought from him July 2021, they are entering their third season this year.
1 gal rootpouch, seedlings were in their rockwool block and moved inside the bag surrounded by inorganic bonsai soil.
View attachment 476313
Rootball from a 1 gal Rootpouch, on their second season.
View attachment 476316