Preferences are applicable per-profile, so if you had changed profiles then it's certainly possible that the gui.update.enabled
preference was enabled in the new profile. That said, that feature doesn't automatically update Wireshark - at least not to my knowledge. What it will do is inform the user that a new update is available, but it's entirely up to the user to decide whether to update Wireshark or not, so most likely either you or someone else who uses your machine chose to update Wireshark, whether that was done through the update notification from Wireshark or completely separately.
In addition, if Wireshark had informed you that a new version was available, I believe it would have informed you about Wireshark 3.4.6, not 3.2.14, since 3.4.6 is the latest available stable release. If you are currently running Wireshark 3.0.14, what do you see if you manually check for updates via "Help -> Check for Updates..."? Does it tell you 3.2.14 or 3.4.6 is the newest version?