I used to use foil as well. I changed to the colander when I was helping a buddy brew pilot beers before he opened his brewery. When we went to sparge, he didn't like the ideal of using the foil for possible off flavors.
Now I couldn't tell you if there are any flavors that may be leeched from this, as I know many home brewers utilize this process with great success. I just followed suit bc the colander is reusable and cost free, and this guy is an awesome brewer who is meticulous with his brewing, so I figured there is a rhyme to his reason.