I travel regularly in the UK and EU with a nail scissors just like the ones in the picture, and have never had an issue. I normally put it, and my nail clippers, in my liquids bag (not sure why, it just seems like the right place for them!), but on the rare occasions I've forgotten, they haven't flagged. The length of the blade is indeed measured from the hinge, so these should be well within the limit.

The gov.uk website lists "Small scissors (with blades no longer than 6cm)" as ok for hand luggage.