Almost all of Tesla's Model 3 orders came from their pre-order queue, which had to be done online (even in store, they simply directed you to an kiosk of their website.) before they even had Model 3s to test-drive. This means that the 78%/82% comes overwhelmingly from the preorder Model 3 buyers, and that as time passed more of the buyers were doing so through the stores.

Consequently, they're not losing "at most 22%" of possible sales, they're losing at least 22% of possible sales, likely more, since they're trying to target mainstream buyers that heavily prefer to test-drive vehicles before purchasing.