I'm not arguing that a flame Bard deals more damage than a Bolt Bard. That might objectively be true. But the stunlock effect of Bolt Bard renders the extra damage from flame Bard meaningless in practice.
Maybe Griswald has level 15 and 6 star runes on his server, I could see that potentially making a difference. But on S5, with max level 12 and 5 star, Bolt is the superior choice. In fact, in hindsight I see that you are on a server with higher rune caps than mine, so that may be a contributing factor.
And one thing that CAN'T be argued with: Bolt Bard will ALWAYS get energy faster than a flame Bard (unless you're doing something stupid like a max starting energy setup, which even then gets wrecked by Bone and will screw you out of more damage from better tertiaries). If paired with the right heroes that earlier white activation can be devastating. It may be true that a Bolt Bard gets less benefit out of her own white than a Flame Bard, the math is ambiguous for me. But an archer that gets an early white? A ninja? A plague? They will be tremendously appreciative of the extra boost to their power, and demonstrate that boost by slaughtering the enemy much earlier than a flame Bard can.
It's the same logic why everyone builds Attack Speed and River on Moon and Spirit Wolf instead of Skill Power and Ocean. Yeah, skill power and ocean will TECHNICALLY do more damage than Attack Speed River. But nobody cares because an Attack Speed River build will ALWAYS activate the stunlock first.