Never heard of using a topper for everything and I don't do it. I do use water soluble for terry type towels but on thinner tea towels and quilting fabrics I do not. I can't picture what she means about the "embroidery foot was going to cause stress and wear on the fabric and possible stretching with knits" . The embroidery foot on my machine doesn't touch the fabric, and if it is hooped, how would that stretch??
So I say she may have been just a supremely cautious person. And with most things, experiment yourself and see what works for you and your machine.