Gary Palmer doesn't exactly exclude off-side play; in my experience, his technique makes it easier to leave the risky off-side deliveries.
I have used his technique to score good amount of runs. I was always weak in the covers regions but can score elsewhere.
Even if his technique makes you predominantly on/leg-side batsmen, why is it so bad? Over the generations, batting technique has become off-side dominant. And, guess where fielding captains place majority of their fielders: the off-side.
Like I said, for me, his technique works well. He teaches how to score runs. I have better than ok against decent club bowling.