No, it is not outside of limitations, but the bleed demand might be too high. Which supposedly is the same reason why the outer slat isn't de-iced. So you may use it if required, but you might encounter other problems after that.
Oh, and of course it is about the 737(NG) which uses hot bleed air to de-ice wings, not any kind of solution.
I guess boeing sees the likelyhood of needing wing anti-ice at that altitude as very slim. Even ice crystal icing only seems to affect engines and heated probes.