Dale, that is true if the poncho is large enough.In pouring/driving rains depending on the soil or forest floor duff there may be splatter along the edges of the poncho shelter that can get on the bivy, your pack, etc. and run in on a groundcloth IF you are using one.
I was a “tarper” for several years in Pennsylvania in the ’70s before I could afford a decent DW tent so I’ve lived in them in rain, wind and snow and sometimes all three in the same storm. I always managed to sleep dry B/C I used a 12 x 12 tarp and had many tie-out points for several configuration options. A great size for one person and barley OK for two in foul weather.

