I think the tadpole serves as a "Chosen One" vehicle as a common but effective fantasy trope. Plus it gives them an explanation for the deviations from D&D 5e ruleset for for pronounced environment interaction = stronger jump, push/shove, throw etc. Still I hope they tone that down requiring some Greatsword Fighter to also throw stuff at peoples just to use that action feels very strange.
As for many familiar things from the old games and them saying they want to be authentic to 5e:
WOTC is mainly to blame for destroying the old Forgotten Realms and the big time shift basically to start with a clean slate. Also many of the 5e changes that peoples unfamiliar will criticize like strict Alignment not really being a thing anymore and removal of many OP/exploity combinations with insane spells and multi-classing.
I would not expect familiar characters everywhere because of the above changes even though they will wake sure to add a few well known ones and other "easter eggs".
