May I ask who gave you that advise? Was it someone who practises TI? The reason I'm asking is when I first started to swim whole stroke a well meaning non TI swimmer at my local pool kept trying to get me to follow an "S" path (he also told me I wasn't kicking fast enough) but I was reading an old TI book titled Swimming Made Easy at the time and decided not to take his advise.
I've just taken it off my bookshelf and I am looking at chapter 7 which has the heading.
Developing an Effective Pull:
It's All about Holding Patterns,
Not "S" Patterns.
Sorry I haven't got time to read the whole chapter at the moment as I'm going to work but I will try and have a recap later.