The main problem with treating or even cleaning suites, settees and fabric chairs is the padding inside the cushion covers or arms and backs. Not only do you need to clean the item but you also need to remove all of the moisture you put on so the item dries without going mildew or bringing up dirt from the padding.
You can see, from the picture above, that there is pading of one sort or anther all over a setee.
Naturally, the cushions have padding inside, they often are zipped allowing you to either remove the covers or get a plastic coating between the fabric and gthe cushion so water and treatments don't contaminate the cushion.
However the arms, backs and facings are all padded for comfort and may well not be removable. The more liquid you put onto these areas the more time and effort you need to remove it. If the liquid isn't removed then any stain may well still be in the fabric or cushioning and may even wick up dirt fromthe inside of the padding.