That's an oversimplified view, the inlet port is side-swept, and the exhaust port is the only one that ever gets swept by the apex seals. The apex seals are only designed to act as "piston rings", though. They seal combustion gasses. The sealing rings around the rotors are oil-control.
The side seals don't seal very well, and fail quickly, which is why rotaries burn oil and suck at emissions testing. Mazda requires a special synthetic oil be used in the Renesis engine for this exact reason. (They may have changed the requirement, by now.)
Here's the construction video:
The big deal with rotaries not making much low-end power or torque is due mostly in part to the fact that the engine itself is a 3:1 overdrive. For each revolution of the eccentric shaft, there is one combustion event, and the rotor turns 1/3 of a turn. This means that 9,000 RPM in a rotary is the spinning equivalent of 3,000 in a piston engine, only the rotary has much less capacity per combustion event and far less weight, moving parts, and complexity. There is also no violent changing of direction in a rotary engine, the rotors spin one way, the eccentric shaft spins the other way. The engine is essentially self-balancing.