I got an email from my bank. "We tried to phone you to clear some issues with a wire you made in the past days, but we didn't manage to talk to you." Of course. I had it switched off. So I called back, but the line mysteriously dropped after the person on the other end said "let me check this... wait a minute...". Twice.
I already had a hunch what it was about, but of course I thought I'd play dumb to extract as much info as possible. An hour later, I tried calling for the third time. At last, I get through to someone who can actually explain.
The problem was with a wire I made to Kraken. Not a big amount by any means - something in the ballpark of Bob's recent addiction buys*

Bank - "We just want to make sure you actually ordered the wire."
Me - "Why? I make dozens of wires, it's the first time..." (Actually not the first: they called once upon a time when I moved most of my fiat to another bank because they pissed me off - but that was to beg: please don't please don't.)
Bank - "I don't know, it's like an automatic system flag... well, it's to some kraken.com."
Me - (Aha!) "I see. So what's the issue?"
Bank - "No issue, sir. We just want to make sure it was actually you who wired the money."
Me - "I did. But now I'm worrying. Is this a scam site or something?"
Bank - "It is some cryptocurrency site, I think... but as I said, it's just an automatic flag. Nothing to worry about, sir."
Me - "What if Kraken sends some funds to me? Will the transfer get a flag too? Will the incoming wire be blocked?" (Slightly implying - should I close my business with you altogether?)
Bank - "Oh no, sir. Incoming transfers are never stopped. There might be some formal issue with outgoing transfers once in a while, but never the other way round."
Me - "I am afraid. I don't want any problems, you see."
Bank - "Just an automatic flag, sir. Thank you."
Things are stirring up, gents. Brace yourselves.
Maybe you are reading too much into it. Banks have alert triggerings of all sorts. Ie:
- Amounts significantly over the usual for your profile.
- Abnormaly high number of tx's.
- Origin/destination to flagged accounts (ie, Bitcoin exchanges?).
- Tx's to/from other countries (this one is the main one when it is not clearly justified considering your informed profile).
- etc etc....
And combinations of the above.
Depending on the alert triggered it may involve a lock of account, a request of confirmation, or a request for additional information.
There are several reasons why banks NEED to do this:
1- To protect themselves from huge fines for not supervising money flow in accordance to KYC/AML and other regulations they are subject to.
2- To protect clients from having their funds extracted by hackers, etc...
3- To know what their clients are doing to detect trends and business opportunities.
etc....
The staff you talked to probably don't know what was exactly what triggered your alert, they just follow procedure (just confirmation in this case) even if they may have some idea based on their previous experience from similar "events".
What do you think would most probably apply in your case for having triggered a confirmation alert?