It's complicated, I think. Lots of car manufacturers DO have some stock of cars, because the market fluctuates. Also , when new regulations come into force, they can play silly games by building masses of cars to the old level of the regulations, and then applying for a derogation to register these after the deadline for the new legislation, knowing that the regulators won't force them to scrap the cars. Right now, there's a big deadline on the 7th of July in the EU, so it could be that whilst the law will not allow them to manufacture to the old regulation after the deadline, it will allow registration of a number of non-compliant vehicles for up to a year after the deadline, provided they were manufactured before the deadline. In the past, this has been a game played by all car manufacturers - particularly if the new regulations involve adding some expensive technology.
Of course, that might not be the reason. The "legacy" manufacturers are also catching up. Tesla is no longer the "only game in town" for an EV, and they have an ageing model lineup...