I always did. But I would think the only wrong would be possibly messing up the bacteria in the tank. But diluted for use then even further diluted from rinse i have to assume its no big deal. Just dont dump a full jug of concentrate down the drain lol.
Now keep in mind laundry and bath water are going to the same place a lot more frequently.
You mean the loose plastic fibers we extract correct? Is it because they don’t break down? If using an in-line filter with paint strainer and dumping a full waste tank of a 100 gallons no problem? We live in the city and most homes have city sewer clean outs. Is there access to dump in septics in rural settings?