Do you think that newalias tried to check every DT member who has security questions? Then PM-ed them accordingly? I don't have a security question for this so that's probably why I didn't receive a PM.
Attempting to answer the security questions will automatically lock your account, because they were leaked with the rest of the DB back in 2015.
Members after that time when it was leaked are safe? Is that correct?
Yes (provided that there were no additional forum hacks after 2015).