Even reset hard wouldn’t delete untracked files. This was a complete overreach by the GUI, performing a clean (and likely a forced one, as git’s requireForce defaults to true).
And they did rectify that eventually, giving a warning, and an option to simply reset. It’s unfortunate this poor person had to be the trigger for that change.
‘git reset’ won’t. ‘git clean’, on the other hand, most certainly does. Even then you have to --force it by default, to prevent an accidental clean.