I mean, with a saucer the very bottom of the root zone will likely stay saturated longer than you'd want, but given how porous the entire container is, it's certainly less of a problem than in, say, glazed ceramic.

When I've used grow bags/root pouches I didn't bother with saucers. But do be mindful of what you're placing the bags on if you're concerned about staining. My practice was simply to move the grow bag to the side and hose down the surface underneath every now and then.

I’ve grown all my veggies in grow bags for more than 15 years. I use 15 and 20 gallon Smart Pots and place them directly on the ground, which is what the seller recommends.. This actually improves drainage and moisture retention. Large indeterminate tomatoes produce roots that actually grow through the fabric into the ground by midseason. I don’t recommend using a saucer with any container grown vegetable outdoors.