Anais From his point of view, it's a serious mistake to use a gafam password manager.
Although I'm not sure why they consider password managers make by "big tech" corporations to be more "wrong" than products made by smaller companies, I assume they might have referred to cloud-synced password managers in general.
In any case, institutions that handle sensitive information that should never be leaked to the public under any circumstance, need to* carefully evaluate the services which they use to store that information. Storing passwords to sensitive systems in a third-party cloud might be considered too much of a risk: An individual's password manager being compromised and passwords leaked means the damage gets contained to that individual**, compared to attackers getting remote access to sensitive data that can damage hundreds of people's sense of privacy if leaked. It's an entirely different risk assessment.
Compromising corporate systems can also be much more motivating to an attacker simply because there is much more financial gain to be earned from blackmailing businesses.
*Or, should. Of course, lots of corporations never take digital security seriously.
**Assuming that the account logins stored in the manager belong only to that individual.