Filler Card (Epsilon Playtest)

There were 16 cards of each 8-1/2" x 11" sheet. The basic land sheet had 3 of each of the 5 basic lands and had this as a filler card for the 16th space on the sheet. The idea was that when you opened your pack of cards and received one of these, you would know that you could have received a playable card but didn't. I wonder why they used basic Islands as filler cards on the First Edition rare sheet instead of these?