I have used 270's on a KLR and a KTM 640 with good results and life. My husky ate rear tires and an MT21 would last 1500 miles.
so I never tried a 270 on that bike.
On a light bike like the WR I see no reason not to run a 270 if you do street and mild dirt. They are soft and were squirmy on my heavy KLR but somehow wore really well. I think low HP helps a lot, and on a significantly lighter WR I think they would wear very well.