Metrolink had to pay extra to restart the production line for the latest build of M5000s, as it had been shut down when Köln and Bonn switched to ordering the HF6. It would have made sense, and perhaps even been cheaper, if Metrolink had ordered something like the 398 from Stadler, or indeed switched to the HF6.
Back on topic, is it certain that the 398s don’t have even passive provision for 750v DC running? 25kV isn’t permitted for on street operation and it’s known that the Senedd have ambitions to eventually use these vehicles as trams across Cardiff, so it would be a huge oversight if provision for future 750v DV running hasn’t been provided.