Yes, because nozzle area is proportional to cylinder bore and number of valves, no matter how small the bore.
There aren’t really very many ways to get more power from a conventional naturally aspirated 4-stroke engine of given displacement. It can made to rev faster and the thermal and volumetric efficiencies (VE) can be increased. With current metallurgies, thermal efficiency (TE) has reached a plateau. There are also problems controlled oxides of nitrogen when combustion takes places on hotter surfaces.
The amount of air the cylinder head can flow will depend on port volume and nozzle area (the size of the valve openings). Opening the ports will improve mid and high rpm torque while reducing it at low engine speeds due to reduced velocity. With only two valves in the cylinder the maximum diameters will be limited by the cylinder bore diameter and valve included angle. Of course the bore/stroke ratio can be increased, but there’s again a trade off in low rpm torque in a very oversquare design.
A very high included angle between the valves will eventually require a DOHC system to operate the valves because a single cam between the two will need excessively long rocker arms to reach them. More weight, inertia and the rev ceiling is reduced. Nozzle area is thus quite limited with two valves. Also, as the valves get larger, heavier and more difficult to control. That either calling for a reduction in operating speed (counterproductive) or a beefier valvetrain (less efficient). If the valve diameter is limited, you have to open it longer and/or higher. But, overlap is limited due to emissions concerns (don’t want half-burned hydrocarbons in the exhaust gas). There are also limits on how early the intake valve may open due to flow reversion (exhaust phase not finished yet) and how late the exhaust valve may close (loss of dynamic compression ratio, reverse flow). Other side effects of a hot cam like this be poor idle quality, and poor torque at low to midrange speeds.
Another problem with a big valve, high included angle design is the shape of the combustion chamber. While a hemispherical design offers reduced surface area for it’s volume, the piston crown will have to be aggressively domed to acheive a useful compression ratio. That’s heavy and that again limits operating speed.
Opening the valves higher instead of longer is another solution, but there are mechanical limits to how high the valve may lift in relation to duration. Of course modern two-valve motors utilize roller cam followers to allow higher valve acceleration, but there are still quite finite limits.
Increase the number of cylinders. Small cylinders have a better ratio of nozzle area to piston area, have smaller lighter components which can spin faster. VE is improved a little and the engine makes similar torque at higher rpm which = more power.
Increase the VE by optimising the combustion chamber shape and raising the compression ratio. Works, but limits nozzle area and thus VE and operating speed.
Use desmodromic valve operation which relies on mechanical levers to control the valves rather than springs. This allows much higher valve lift for given duration and also decreases parasitic losses in the valve train, improving midrange torque. Try and catch a Ducati on a mountain road and you’ll know what I mean.
Use a valve control system to either vary the valve lift, duration or timing, or a combination of these. VTEC, VVTI etc. Allows the use of more aggressive valve motion at high revs while mitigating some of the effects at low and midrange speeds.
Use mulitple valves (up to nine valves per cylinder has been tried) to increase nozzle area and reduce the weight of individual components. Allows mild timing and lift to be used while improving flow over that of a single valve and also higher operating speeds.