I think "younger" here is meant more as "not old." 16 year olds are less safe drivers, yes, but on account of the price they're not going to be a big part of Tesla's demographic.

Since there's no affordable model, and they're a newfangled gadget with strange refueling infrastructure and a giant touchscreen for a console, Tesla owners probably skew toward middle aged. So they'll have fewer drivers in the less safe age ranges at both ends of the spectrum.

That depends on how you define younger. Not many teenagers can afford a Tesla though so in this case younger probably means mid 30s to early 40s. That largely removes very inexperienced drivers and the elderly.

Risk by age decreases from 16-25, bottoming out from 30 to 40, before increasing again. 30-40 is, likely, a huge part of the Tesla demographic.