Similarly, no HR department will inform another HR department if you were fired or why, they'll only confirm dates of employment.
Telling you something that they think about you, without witnesses, is not slander.
e.g.
> Typically, the elements of a cause of action for defamation include:
> A false and defamatory statement concerning another;
> The unprivileged publication of the statement to a third party (that is, somebody other than the person defamed by the statement);
> If the defamatory matter is of public concern, fault amounting at least to negligence on the part of the publisher; and
> Damage to the plaintiff [from the statement itself].
https://www.expertlaw.com/library/personal_injury/defamation...
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IMO, there's two reasons why they won't tell you why you're suspended:
* It may help bad actors figure out how to circumvent the system (but, trust me, they already know!)
* It may reveal their own wrongdoing.
In general, businesses don't need to do business with you and can exercise relatively arbitrary judgment on this. It gets scary when we're talking about entities with significant market power just deciding to exclude you, though.