Hi Steph - I'd agree with that. Perhaps if you just had one thing published on an obscure ezine it wouldn't be worth mentioning, but if you had a few bits and pieces published, that would start to look like a portfolio of work, and I think would make an agent see you in a good light. Shows signs that you DO actually write, for a start! And also of a degree of talent, dedication, self-motivation, etc.
Jane x