Blood Sacrament channelling duration breaks on reaching max reserved life in non-stop channelling

I have Blood Sacrament, from Relic of the Pact, set up so that it reserves 33.26% of my life per cast with a 0.19 second case speed.

And after equipping a medium cluster jewel with the notable "Enduring Focus", which gives me 25% chance to gain an endurance charge every second I channel.

But after trying it out, I noticed a possible issue:
I do not gain any endurance charges with this setup.
If I remove the support gems from Blood Sacrament and return to a much lower reservation cost per cast then Enduring Focus works and I get endurance charges.

So it seems that when Blood Sacrament reaches the point where no more life can be reserved, where it auto-casts the explosion, it stops channeling. Even if I never let go of the button and my character is already channeling the next explosion.

Is this intended or is this a bug?

(I have not been able to test this yet, but I assume it will do the same thing for the "Swift Killer" Trickster notable.

Repro steps:
- Equip Relic of the pact with the following support gems: Arrogance (level 1), Lifetap (level 1), Increased AoE (Any level)
- Equip 2 Essence worm ring. (You should now have a reservation cost of 33.26 on Blood Sacrament
- Equip enough cast speed to have ~0.19 cast time on Blood Sacrament.
- Equip a medium cluster jewel with the notable "Enduring Focus" and
- Start channeling Blood Sacrament and do not stop.
- See if you gain endurance charges.

Bug report reference number: 791999409
https://imgur.com/a/fjXtjco