Agreed. If you run the feed rather lean you can get away with that method for a while, especially using a media with a high cec, since the buffering capacity of the media can hold onto or bind some nutrients that aren't used.
Promix or other peat based mixes are excellent for this since they give you a bit of room to mess up. It cushions your feeding mistakes.
Coco tends to bind calcium and magnesium, but I don't believe it has much exchange capacity for other nutrients compared to peat mixes.
All that said, it doesn't take a ton of runoff to prevent problems. As little as 10% runoff for the last couple feeds of the day can be enough if you aren't overfeeding. If you are really concerned about wasting the runoff, use it on houseplants or outdoor plants. Or depending on the size of your system it might be worth using a sterilizing UV to clean the runoff so it can be reused. That's what I do personally and don't waste a single drop of water.