yes short barrels can make the required power and accuracy...... but..i 'think' that longer barrels are more forgiving of variances like pellet fit and weight.
i believe that a longer barrel does the job of a short one PLUS the last few inches are for calming [via friction] the pellets,
for example [and this is just made up waffle to highlight my thoughts] say you need 6" of barrel length in 177 to get the required spin/accuracy and power..going shorter drastically loses power and accuracy........ now then, if you have a 10 " barrel then the last 4" are to utilise the lower [steadyer] pressure of air [piston has pretty much finished moving by now] to calm the pellet before release, meaning less fluctuation between pellets [variances in tightness/release point etc] which in turn increases accuracy imho