Nope - definitely not true - they don't have many big tables, but they do have a few. We had a PS for 5 last Dec - no problem!
We also had a PS for 5 for the the PSB last Dec - they told us they had no more tables for 5, so we would have to take 1 table for 3 and one for 2, but would try to make them close to each other. When we arrived to check in, we were shown to a table for 5 - no problem!