Yes, I think it may play a role that the players at the top are more adaptable or may already have experience with the map. But I don't think those scores should be disregarded as evidence towards side B being less luck based. It's just not conclusive.
It's quite clear the effect that luck has on elo, when I play a lot of spiritless games I can reach master rank but that probably wouldn't be possible with only spirit games, too many games lost because of the imbalance and asymmetry.
Playing real time certainly helps for reaching the top in arena, because you can grind much faster, and with the way the system works, it's advantageous to play a ton of games to climb over time and get on good streaks.
With that said, Frogodo, Ellektra and andyxdz all won their arena seasons playing largely turn based, if I'm not mistaken. While the average level of play may be higher, if you take the time to think of your moves you should still win the large majority of your games. The difference is that you may only have a window of maybe 100 games to do that (depending on how much you play), whereas those who play real time can put out a lot more games.
I think that to win arena you have to be really invested in it. That's why I still haven't taken a real shot at it. My first two seasons I played only like 30 turn based games and was content reaching the top 20. To make it to the top, you'd probably need at least 100 games while maintaining a 90%+ win ratio. It's doable, but the season being only 90 days, you need to be really dedicated to it, remind yourself every day that you need to get a new game going.