But will it? Unless I misunderstand, the assistance is limited to twice the rider's input. So if, you have a 250 watt motor and can only pedal 100 watts, then you only get 200 watts electrical assistance, not the full 250 of which the motor is capable. Fro what I gather from other posts, the Panasonic Company did not set out to make a world beater system, just one that copes with odd Japanese laws. Because it works very well and is reliable, it sells in Europe.
It's quite true that the more capable riders can extract the most power from the system for the reasons you give in your example.
Sticking with your example, say a rider can only provide a maximum 100 Watt pedal effort for a short continuous period, say when climbing a hill. They are therefore likely to be outputting about 70 Watts for a sustained period on the flat or gently undulating terrain. If the Panasonic system is set to 1:1 assist, then the 70 Watt continuous rider effort will be 140 Watts at the rear wheel ( neglecting efficiency losses). When the same rider comes to a hill, the pressure on the pedals starts to increase, so his power output will do the same rising to his maximum 100 Watts. The Panasonic system will sense this extra rider effort through the torque sensor on the pedal shaft and raise it's power output to match. The power at the back wheel will now increase to 200 Watts.
This is quite a simplistic example. The power delivery from the Panasonic unit varies continuously depending on the angular position of the pedal crank. It can peak for short intervals at several hundred Watts, but the above is roughly how it works.
The important thing is, how it feels to ride. What the user experience is like. To me, the Panasonic system fools me into thinking that I am a superhuman cyclist. It is that subtle and unobtrusive. When I get to a hill and my pace starts to fall back, it feels like I am falling back into a helping hand that collects me up and pushes me along. Again cleverly kidding me into thinking that I have found some sort of second wind.
The Panasonic unit isn't a quirky Japanese system that has been crowbarred into a European bike. It has it's origins in Japanese law, but it works very very well on our bikes. It may not suit everyone because it tends to reward low cadence and higher pedal pressures and this may be at odds with seasoned cyclists.
Sticking with legal motors, you will be off and walking up a hill with any legal hub motored bike long before you are with a Panasonic powered machine.