I guess it makes sense to differentiate their EV models. Looks like the 45 will be the first of the cars under the new name
www.autocar.co.uk

Hyundai previews new Ioniq 5 EV ahead of February unveiling | Autocar
New model sits on Hyundai and Kia's first dedicated battery-electric car platform and is first to launch under new Ioniq sub-brand