yep, it's true they teach English teachers to not use the L1 (native language) in the classroom. All English lessons even total beginners in English. If they can't speak a word just mime, draw etc to teach vocab and a few simple phrases....
I guess some transliteration would be of benefit but that's my opinion....I remember being taught some obscure African language as an example hy a EFL tutor. She just used objects (realia), mime, acting, and drawings on the board to teach vocab...