You can't really call 1.01 a sure bet either. In fact, a 1,001 bet is not a sure bet either, the chance that it will go wrong mathematically is about 1 in 1000. If you then place 1000 bets, in theory it will go wrong. But in your mind you start each bet as a favorite with 1 to 1000. There are a few examples of people who have bet on a team that was leading 4-0, and because it went 4-4 they lost a lot of money.
1.01 is usually referred to as a sure-bet in sports betting even if it technically isn't as you explained. It's pretty obvious that there are no sure bets since such bets could ruin the house in the short-term and long-term.
100% sure-bets are actually possible through arbitrage betting, but the catch here is that your account could get limited or banned pretty quickly of the house notices.