Tristana E not charging off ult

Was that intentional?

I've been searching through patch notes through the past year, and I haven't seen anything about that specifically not charging her E. I feel like there'd be a note in the ability that says it doesn't charge it, especially since the spell itself says autoattacks AND abilities charge her explosive shot.

Did I miss it? If it's not intentional, I'd love to have it actually work. Who knows how many kills I've missed because I didn't charge that last shot before ulting them away.