I'm not sure of the point you're trying to make, but I'll bite. Fixed-income securities that instantly come to mind are government bonds. I have no idea of what governments invest in -- jackboots for their thugs, most likely. If you're suggesting that fixed income funds trade currencies, I'm sure many of them do. But invest in currencies? Lol, no, never.
Well, I said apart from derivatives and bonds (I was trying to be helpful, honest), so I can't accept "government bonds" as an answer (I hope you'd realise that they're just a specific form of bond). No, I'm not suggesting that fixed income funds trade currencies (though obviously they will), I'm saying they hold currencies as an investment for their clients. Fixed income traditionally was investments for "widows and orphans" - low risk, cash and bonds, in a pre-derivative era. So that's BTC investors, widows and orphans now - you want to tell them their investment isn't an investment, or shall I?
(I'd really like to stay and find out about your interest in Jeffrey Dahmer, beanie babies, why you think I'm Ted E Bear (and your interesting views on how forums work), why you think I might lie about being a bad trader (and how my personal involvement with something might completely invalidate that thing if I wasn't really involved - sorry, I quoted your post before you edited to add that "K" part - but I caught it later and smiled, honest!), your other theories and how they all relate to the topic of investing in currencies, but it's late on Planet Earth and I need to head off. And I fear that rabbit-hole would be too deep.)
Edit: Tell these guys too. And Barclays too. And these guys should definitely know better.