In what way?
Well, Steam has 2 usernames for your account: Your Login and your Username.
Once you set your login, it cannot be changed. Also, older steam accounts have their emails as their logins. I’m thankful I got an actual login, though. They did the exact same database mistake as PW.
Your username can be changed at any time you want.
You also have a steam account ID (quite a lot of IDs…), for example #76561198261097951.
Now, PW wants to add display names that are freely changeable. So that brings you to the same 3 identificators as on Steam: Username (Login), Display Name (Username), and Account ID (SteamID).
Seems like when PW was created, the devs would learn from Valve’s mistakes and not create a database where the keys are usernames instead of IDs. But well, seems like we’re stuck with our usernames until display names arrive, if they even do arrive.