Pattern planes have tapered wings because they look nifty- Period
Pattern planes are NOT form follows function models
Tho some think that -- they are simply a very slowwly evolved art form.
There are some really silly features in some pattern designs ( large noses to slow down lines (?!)
The part which makes em work well - for the most part is they are lightly loaded and have good power to weight--otherwise -they will not fly the patterns
it is that simple.
I f you have built a few hundred and designed many which have won nationally and placed internationally - let's hear your arguments to the contrary.
They are - fun to fly -and for the most part easier than most scale designs but a rectangular wing on a Pattern plane works just fine.
Lowering the wing loadings cures 99.99% of any of the problems with planform on a good aerobatic model