When Jews found out about news of Allied victory, were hiding Jews able to simply come out openly in safety? Why might that not be the case?
How did they know that this, or other information, wasn’t just a ploy to root them out?
It was safe for Jews to reveal themselves in German occupied territory only when the Allies had not only occupied the territory, but disarmed the local Germans, and established the rule of law under non-German auspices. Not before. Some people "revealed" themselves before this, and some paid the price, as related in books such as "The Last Jews of Berlin."
There was a fair amount of "seesaw" fighting in Europe, even during the last days. The only real safety before the establishment of Allied control was achieved might have been to retreat in the direction that the Allied troops were coming "from." There was no guarantee that newly arrived Allied troops would be able to hold on to the territory that they had just liberated. Unless the troops had moved on voluntarily, other than the military police.
The Nazis were "die hards" who used every trick in the book to last as long as possible. For instance, a group of SS men sewed Stars of David to their arm bands, and pretended to Russian liberators that they were Jews "impressed" into German service. This trick resembled Germans masquerading as "American" soldiers during the Battle of the Bulge to hinder the Allied response. The SS men were slaughtered when they were unable to authenticate their Jewishness with knowledge of religious passages such as "Schmaa Israel." And German guards sometimes continued to abuse prisoners in concentration camps after Allied soldiers had arrived and ordered them to stop. They had to be disarmed.