Thrilling Chase benefits are unclear

I just took Thrilling Chase and was only using Explosive Spear to consume frenzy charges but it does not appear to benefit Explosive Spear in any way. I can't tell what the "Benefits" are for Explosive Spear so I can't tell if this is a bug (I would assume bigger AoE, or duration, possibly damage?) or if the only "benefit" is instant explosion which... can't really be doubled?

I tested it with Lightning Spear and it seems to only double the number of Splits from 3 to 6 sometimes. That's the only line on the gem that talks about Frenzy Charges but you'd think that since Explosive Spear has a whole tab labelled "Frenzy-Charged" that those lines might be effected?