A. I've fallen victim to some kind of malware scam.
B. I briefly installed Electrum when playing around with Bitcoin back in 2014 and it's somehow defaulted to those setup details (although none of my regular passwords are working),
C. It's a bug (unlikely).
I think option B is most likely in your case, even if you remove a program, Electrum files stay in the default folder. When you install a new version of Electrum it is just open you old 2014 default wallet which is password protected. If you save seed from that wallet it is easy to bypass password problem by recovering wallet with seed (wallet will be password-free). I would reject the option A since you verify Electrum files.
The alarming thing is I installed Electrum on my work computer today, clicked Next on default_wallet and the password/seed key setups screens DID come up.
This is because there are no
old files on your work PC, Electrum just gives you option to create a new wallet.