Those who took test rides at the Reveal Event mentioned they saw T-Slots:I think this will confirm once and for all that the lines in the truck bed are not T-tracks but rather raised up plastic runners to help with sliding items into/out of the bed
Could be that there are optional hard rubber plastic inserts that could be placed in T-Slots when they're not frequently in use - to keep crud, rocks, and dirt from getting into them. Maybe someone who was at the Reveal Event could chime in and let us know what they saw. An article on Teslarati does reference T-Slots (but they might not have the best information either).
Or, as some have suggested, maybe there was a change in the prototype since this photo was taken at the reveal. In any case it will be nice to see the Second Reveal whenever it happens, to confirm this and see what other changes they are making.