This story (which I know is true) always made me nervous, for the reasons you suggest. There are only a few times I’ve needed to protect myself from online (or offline) behaviours but it means I do recognise other’s self-protection measures.
Back in the early 2000s I helped organised an online conference. One speaker liked to be known only by his last name but he later explained to me that I blew his cover by listing his full name online. That enabled his overseas estranged family to trace him. Luckily it was a positive reunion, but it taught me an early lesson about the fragile nature of privacy in a connected world.