What does this email from AirBNB even mean?

[Aaron86]

I just received an email from AirBNB informing me that an authorization of $400 that had been placed on my credit card "has now been voided." The weird thing: This email is in reference to a trip that I took more than three years ago. Why would AirBNB send this to me now and what does it mean? 

On Apr 6, 2017, at 7:52 PM, Airbnb <automated@airbnb.com> wrote:

Hi Aaron,

The authorization of $400 that had been placed on your credit card (AMEX xxxx) for reservation zzzzz at yyyy has now been voided. While this authorization void is immediate on our part, it can take up to seven business days for it to show on your statement.

Thanks,

The Airbnb Team

[Jenny135]

@Aaron86,

@AirbnbHelp wrote in Twitter a few hours ago "If you've received an email regardring an authorization void, this was sent in error. No action was taken on ypur account, please disregard"

[Matija33]

Just received this same message after host didn't respond to my booking after 24h.
Message is confusing, and if it relly is an error its a shame it wasn't fixed since 2017!