Growing up my parents once found a piece of glass in a sauce jar....bottom line is things happen during manufacturing and you never know what could get into a bag of pellets. IMHO it is better to be safe than sorry.
Generally speaking, food is MUCH safer than wood pellets! At least I hope it is.
Bill
I used a funnel from the automotive section but the duct boot seems like a great idea... How big is the plywood platform?