My teacher says play with tension

I'm learning the pathetique sonata 1st movement and doing pretty well. But my teacher says to play all notes with forte and let it tense up. The surprising part is, that he said is to play with tension and bad technique. He said feel all tension pain and then you will easily play without tension. He also says my wrist is very relaxed, then he said forget about technique now, make your forearm tired .what? is he red flag(wrong) or ball knowledge(true)?