I am not sure why it would be full of anything; if it was full, i would wash it and empty it, and then it would be empty again. If it wasn't full, I'd put some dirty towels at the top and run a load. Also why would I be dangerously low on towels all of a sudden? This is also how I approach dishes in the sink.

I have a feeling that the people who are very concerned about not blocking the resource (i.e., the sink) have to deal with more randomness in their routines, maybe because of sharing the resource with other housemates or family members, or having a more unpredictable schedule, and I can respect that.