Also This strange trend to split username and password on to two separate pages, or only showing the password field after confirming the username

This is because of Enterprise Single Sign On. You can try this for yourself by going to gmail.com and enter the email of a public person at a large org, for example the CEO of Doordash ([email protected]). After you enter the email, you get sent to Doordash’s employee portal to authenticate. Based on the email you provide, Gmail has to figure out if you need to provide a password to gmail itself or if the email authenticates another way.

It’s not like you can’t add a “Log in with your company’s SSO” button to the form. That works just fine and at least Microsoft does something like that.