I think cleaning a rat nasty catpet as effectively as can be done is better and healthier than cleaning a relatively clean carpet and leaving nasty/toxic residues all over it. The latter is unfortunately more common than the former and little mentioned unless it is so bad that their dog's face swells up after you leave...
The main goal of cleaning carpet in that condition has two main points that need to be confirmed before you leave that residence
1. After the treatment of carpet and proper rinse agent is used, you need to make certain the water you recover smells as clean as the water that was used to flush it out. What do I Mean by that? Once you go over the concerned areas, pull the vac hose off your wand and smell the water inside your wand. If it smells like funk, keep rinsing until that water smells clean. That tells you there's no more funk on the exposed carpet
2. With all the flushing and SEVERAL dry passes, a fan needs to be put on that carpet to speed up the drying process to prevent any heavy wicking
I don't care what the attorney wannabe Fred says. This cleaning process is so much better than just leaving it for the customer to handle, whether it be them pulling that carpet up funky to expose them to the hazardous funk or even the customer going out and renting a rugDR to make the situation really biohazardous
Hell, in the past I was asked to clean a carpet after a landlord kicked out a HOARDER just so they wouldn't feel dirty pulling up the carpet to replace it, which I did clean it.
You'll run into several of these situation in the near future, so feel free to make the judgements for yourself. Just remember that what your goal of what condition the carpet needs to be might not be the same goal as the customer as long as your machine can perform the needed pressure/vacuum/heat to clean in this scenario