1. The fan turning on only at certain temperatures is not BS. It is there to reduce noise and to save (a little) power.
2. Playing games will cause your CPU and GPU to heat up. Whilst your PSU does have more load and will be producing more heat, it will not be even close to the same as GPU idle vs GPU under load
3. The heat generated by the CPU and GPU will not get vented straight into the PSU, it will be exhausted. The case has airflow and it designed to expel heat, so the system won't just keep getting hotter and hotter, under load it will reach a maximum temperature.
4. Depending on what you are running, the load could be extremely low, so you have very little heat being generated, or it could be very high load, at which point I would be worrying about the fan not coming on. With a 700W or your now 800W unit though, we are talking crossfired 7970's + quad core CPU all overclocked, several hard drives and several fans for it to be under heavy load
5. What were you using to read the temperatures? The temperature you were looking at was most likely the graphics card. afaik, no Corsair PSU has temperature sensors, so you won't be seeing the temperatures. I would imagine the protection would be kicking in before 90 degrees anyway and shut the power off completely