While I agree that there could be a lot of authentication prompts to deal with, keep in mind that the frequency and kind of notifications you get depends on sec

While I agree that there could be a lot of authentication prompts to deal with, keep in mind that the frequency and kind of notifications you get depends on security requirements of the operation/flow you're in and are not indicative of the "quality of SSO implementation". Some high-security flows use auth tokens with short TTLs (e.g., 20 mins). Some flows may trigger "less secure" "pick a number" notification (user is prompted to tap 1 number out of 3); some flows trigger "enter a number" notification, when user has to enter the number they see on the login prompt (I personally hate this one). Some of these things are controlled only by service (e.g., TTL of the auth token), some I suspect could be tweaked by the tenant admin (e.g. pick vs. enter a number).