This is no surprise. The US offers now higher interest rates over the whole yield curve than is offered on HIVE savings (i.e. less than 2.9% as of now). Also, higher FED rates mean less USD in circulation, while higher rates on HIVE savings are achieved (if I got it right) by creating new HIVEs out of the blue. No surprise the USD is stronger than in April.
April 2022 may have been the worst moment to start such an experiment because it coincided almost perfectly with the tightening cycle of the FED. Repeating the experiment in mid-2023 when the FED will stop hiking (and other central banks around the globe will continue raising rates to catch-up and strengthen their own currencies) should get you to very different results.