The UK could have looked at the evidence and decided it wasn’t a crime according to UK law and hence he shouldn’t be extradited. I haven’t looked at the evidence for a while, but last I checked I didn’t even understand how his actions were a crime according to US law.

So yeah the UK has leeway here. Why pretend otherwise?

edit: Why would I receive downvotes for this?

https://www.gov.uk/guidance/extradition-processes-and-review...

Extradition hearing

"""

The extradition hearing before the District Judge is where most of the issues in the case are decided. The CPS will represent the requesting State in the proceedings.

The judge must be satisfied that the conduct amounts to an extradition offence (dual criminality), that there is prima facie evidence of guilt (where applicable and in accusation cases), and that none of the bars to extradition apply, including that extradition would not breach the person’s human rights.

"""

The judge could both not believe that dual criminality is satisfied and could also believe the supposed evidence isn't good enough.