Yes it's a not insignificant problem, I discovered this by chance a while ago, when I "accidentally" booked for 1 and then noticed the rate had dropped...
Yup. I've learned to check the rate for 1 and then for 2 to see if there's a difference. The SEA Hilton has charged extra for 2 for as long as I can remember and most recently I noticed that the SEA DT was doing the same, at least for the rate I was using. I prefer to reserve for 2 if there's no difference so they give me enough breakfast vouchers, room keys, etc.