If it did say that it would be a typo.
Yes, I thought so too, and said so to Mrs ONB. Then she showed me the webpage she had seen. I then searched the site and found
Hand Baggage Allowances.
This was a different page to the one she had showed me, but it says exactly the same.
So I called Customer Services, got through promptly (now there's a first), and was told that the allowance is indeed 23Kg per item, for 2 items of hand baggage, ie 46Kg in all. I asked her several times to confirm that is is correct, which she did.