What do you mean on purpose? So if I had a Blue wallet, and I wanted to check my seed (for whatever reason), the software would show some random words (aka a fake seed) and not my actual seed? Why would it do that? Could I still bypass it and have the client display my real mnemonic as well by entering another password or removing that feature in the settings?

It actually doesn't sound that bad when you think about. You enable a feature that displays a wrong seed. If someone were to get hold of your wallet file + password, he wouldn't be able to spend from the wallet or display its seed without a secondary spending password. Some exchanges use a trading or withdrawal PIN that is independent of your password.