I hear that. But if you presume they will need to work on demand at some point in the next 3 years, which I think is a reasonable assumption, do they dare wait until the very week they NEED to work on demand? Is that not too late? That is why start slow with an introduction campaign.
You can head off the "Tesla is desperate" story line by just laying out the strategy ahead of time. Say they want to gradually work on the campaign, so they are doing the prudent thing and feathering in to build brand awareness.
Imminent Model 3 volume production is when IMHO they should start if they don't have sufficient deposits anyway to sell out for the foreseeable future already. They can then rely on the laurels of the Model S/X to promote their high volume car.