A lot of FO guys witnessed what Luke did. (More than the troopers who saw Obi Wan vanish, but those guys all got shot.) Gossip spreads pretty fast. The FO will find that a lot harder to spin doctor than rumors of a lone defector.
Will they care though? And even if they did, will that necessarily spread from there throughout the entire galaxy? Even if it does, that seems a pretty weak premise to rely on for the sole reason why the Rebel Alliance proper is able to reform. So the Resistance couldn’t convince other systems and factions to support their cause, especially after the atrocities the FO commits in TFA but somehow word of Jake Skywalker via the mouth of his enemies is supposed to somehow win people to the cause of the Rebellion? And this is the Luke Skywalker that in TFA is relegated to myth and legend like Han and the other characters are?
Sorry but I don’t buy TLJ’s depiction of hope renewed for the galaxy as none of it makes sense or has enough impact to make it believable.