This has been a problem since the game came out. Firebreak seems like the only character whose kill based specialist ability never gets featured as the best play of the match. A lot of my friends play Prophet and it seems like their Tempest kills get play all the time. Even characters like Ruin, Seraph, Battery and Ajax don't seem to have a problem getting featured, but I've played Firebreak for probably 75% of my ~8 days of play time and I can't remember a time I've ever gotten the best play with the flamethrower.
This link is the worst I've seen. A 9 person feed overtaken by a 3 person feed. I know the whole 9 person feed wouldn't have fit in the best play, but there had to be a stretch of kills in there more deserving than the one that got featured.
The " logic" for play of the game are flawed anyway.
Ww2 had the same. Than multiple people tried to find out the logic.
In ww2 it wasn't amount of kills, xp earned, medals, headshots.