I suspect the warnings are because the one that has escaped is habituated to humans and as a result is not as inclined to avoid them, but will still revert to instinct if cornered.
Wild predators tend to have great aversion to humans since we have hunted them for millions of years, so they will stay well away from us given the chance. The odds are that virtually no-one would ever see one if they were re-introduced.
I also think have a rather strange perception of risk from wildlife in this country. Virtually everywhere else in the world lives with significant predators - there are lynx, bears and wolves across Europe, plenty of big cats across Asia, Africa and the Americas, plus the large reptiles, sharks and so on. Often in very close proximity to humans. Human fatalities from these are tiny in number compared to those from other humans or our creations, like cars.
We have co-existed for millennia and our bath-tubs are more dangerous :-)