At least you have SSO! Imagine what if you had different credentials to each of these services (even logins)! There are big companies that operate like that...

Having different credentials would actually be faster. One key chord to ask 1Password to fill in my password and log in, and I'd be done. Instead, with SSO, every time I need to log in, I need to type in my email address, go through a bazillion redirects to Google where it asks me which of my accounts I want to use (even though I already typed in my email, and even though I only ever use one of those accounts for SSO), click it, often have to then enter my Google password and/or OTP code, then go through a bazillion more redirects back to the app.

There are also lots big companies that have "SSO" but it is half-baked or incomplete with regards to which services and you end up with MSSO - multiple single sign on.

Install 1Password and it's basically like having SSO.

And why shouldn't he have different credentials? A password manager would make this a cakewalk.