Think he means drain to waste, as opposed to drain to reuse. The real benefit from coco is with a quasi-hydroponic setup to give roots easy access to liquid feeding. Use coco with small pots, super root bound plants, feeding 4-6 times per light cycle. Go straight coco, or coco/perlite mix. I dunno if I'd go with mixing soil/coco because you have the negatives of both, when you could only have the negatives of one and indoor turnover is so short that compacting/aeration really isn't a problem. The coco/soil mix will promote a root bound plant, but a root bound plant is only a positive with a hydroponic setup, which is the better way to go btw. If you feel like buying hydro stuff and playing around...
https://www.hydrofarm.com/p/GFO7CB
https://www.hydrofarm.com/p/GFOE2
https://www.hydrofarm.com/p/GFO7CB
https://www.hydrofarm.com/p/GFOE2
