Edit: acd10j says I misread. I still think they're working on full reusability, but that's just my guess, not an announcement.
Relevant paragraph: The medium-lift Neutron rocket will be a two-stage launch vehicle that stands 40 meters (131 feet) tall with a 4.5-meter (14.7 ft) diameter fairing and a lift capacity of up to 8,000 kg (8 metric tons) to low-Earth orbit, 2,000 kg to the Moon (2 metric tons), and 1,500 kg to Mars and Venus (1.5 metric tons). Neutron will feature a reusable first stage designed to land on an ocean platform, enabling a high launch cadence and decreased launch costs for customers. Initially designed for satellite payloads, Neutron will also be capable of International Space Station (ISS) resupply and human spaceflight missions.
Of course with Neutron not expected to launch, even under Rocket Lab's target, before 2024 they may have answers for a lot of this. I see nothing about fuel for example, maybe they've been working on their own great methalox design. But either way, F9 isn't going to be the comparison by the time they really get going.
https://www.cnbc.com/2021/02/25/relativitys-reusable-terran-...
Relativity is claiming to be working on a fully reusable, Methalox burning, competitor to the Falcon 9. Of course Relativity has yet to put something into space so Rocket Lab seems better positioned but these companies are all competing for the same funding and launch contracts so they can’t sit back and let another company steal the lime light for long. Really exciting times in the space industry, the US could have four different companies making reusable rockets in the next 5-10 years.