Actually what a safe bet means depends on your definition of the word "safe". Because if you mean by safe bet that it should always win, then there is never ever a chance of that unless you have some fixed matches and know the outcome already. If safe bet means it has better higher chances of winning than the odds suggest then surely you are going in the right direction as I have often seen odds provider being poor especially on events like UFC where I have often seen that they give grapplers a lower chances while in reality grapplers win more fights than boxers and now days they pay more respect to grapplers because of the submission threat.
So, make sure what you mean by a safe bet because the term betting itself means there is always a chance to win or loose even if you blind pick a bet or you have deep knowledge it can still win or lose.
You are right because it hasn't been stated nor clarified about on the word "safe" yet it can be classified into two things which one do talks about guaranteed win and one will be indicating about higher chance of winning even though its not completely safe due to risk of losing but it can be considered out.
Safe bets or 100% win does really exist on fixed matches where we know that these informations cant really be attained or known by average bettors but on general theres no such thing
about thinking to be on the safe side once you do really involved with gambling.
People do still think that they can make theirselves rich into this industry but once reality slapped up their faces then they would really have that different input.