First, for someone who has been playing chess competitively for the last twenty years, none of the results of the analysis is a revelation. Like so many "data" posts that seem to be in vogue, this one states quite the obvious viz the game of chess has evolved and has improved in quality. Hence opening colour matters, games are longer and many end in draws. DUH!
As a secondary point, the OP makes a big show of the "steady increase" increase in length of game from the 1970s. On closer inspection, what is implied is that the average game has gone from 37 moves to 42 moves. For a chess player, that increase is hardly significant and can be attributed more as a result of prevailing opening theory and chess playing style than reflective of anything else.
A clear case of data-blindness.