https://support.google.com/accounts/answer/1721977?co=GENIE....
That doesn't mean more than one account per person is OK though. Just the reality than more than one person may share a device.
Lots of screenshots around if you google "Google Account Chooser".
Pretty much everyone who works for a company that uses GSuite will be very familiar with it.
Google gives free storage, etc per account. I wonder, if you exceeded that and had a second, how quickly they'd say 'one account per person'?
One possible explanation is that the exit IP for the company has had malware hosted on it, so that IP is getting banned from Google services. If they go home or turn off WiFi on their phones it will probably work.
Fully believable.
In some cases people don't even have the slightest clue.
In this case there is at least an explanation even if it is bad.
PS: I don't hate everything Google do or any employees specifically, I just try to shine a light on the places where they fail like lack of transparency or even basic communication or their abuse of market power to try to kill competing browsers.
They have done good work in other areas it seems like standing up against dragnet surveillance etc.
For the few Google products we use at work, like Calendar, we make sure that people do not register with their existing personal accounts but use their work email address.