I think it's possible there's a short time lapse between death and a body's disappearance, which would explain the corpses that were found in The Many Deaths of Toa Tuyet. Of course, it's possible that the Ta-Matoran and Le-Matoran Tuyet killed had too much damage done to their bodies to be teleported, but the Ga-Matoran she drowned should definitely should have been teleported, since Mavrah died the same way.
Well let's look at what the story said.
Lhikan knelt down beside the still, ruined body of the Ta-Matoran. He lay where he had fallen after a vat of molten Protodermis had inexplicably tipped and spilled its searing contents on him. It was an awful way to die.
According to the "brain has to be intact" theory this one is likely ruled out for the Red Star. I'm presuming he would be standing when this happened, and the head would be the first melted -- at least it's the most likely scenario.

The first rays of dawn had illuminated the object in the road now, and Kongu could see it for what it was: a dead Le-Matoran, mask shattered from a fall.
It's possible the impact destroyed his brain enough to count. Depends on the fall and the makeup of the brain. The mention of the mask shattering, but not any other detail makes me wonder if the head hit first (and if that might even be intentional?

).
He was even clutching a tablet that was intact. Dunno if Tuyet put that in his hand afterward or not, though. The first one was too, and I don't think that tablet was damaged either as far as is mentioned, so that might not help...
But just thinking it through -- since we know corpses disappear (and this must be common knowledge), and we don't know how long the time delay is, if any, and we know Tuyet was putting tablets in their hands (my point not being about whether before or after the killing but that she needed the tablets found in their hands to set up the DH threat cover story), if she let them die in a way that she knew enabled them to disappear, her goals would fail. She needn't have any clue
why bodies typically disappear. But she
would need to make sure they die in ways that destroy the brain. Otherwise there's no corpse to hold her tablets.
Presumably over the course of the extremely long history in Bionicle someone would have figured this pattern out, and she heard of it.
It took longer than Lhikan expected to get his tasks done. Night had already fallen by the time he made it to Ga-Metru. Nidhiki was there ahead of him, standing with Toa Tuyet amidst a crowd of Matoran. A Ga-Matoran was lying on the ground, unmoving. From the puddle around the body, Lhikan guessed she had been fished out a canal. In her hand was the now familiar stone tablet bearing Tuyet's name.
"What happened?" he asked, already guessing the answer.
"It was awful," said Tuyet. "I heard a scream and a splash … I ran out … but she was already dead. Drowned, with that … that terrible reminder in her hand."
"Just like the others," Nidhiki said, his eyes meeting Lhikan's for a long moment. "Tell him when this happened, Tuyet."
"Only a few minutes ago," said the Toa of Water.
At first glance this one seems to contradict, but notice the context -- it only happened a few minutes ago. More evidence for the time delay; presumably this corpse did disappear later.
This could minorly contradict my above reasoning too, but notice a crowd gathers in just a few minutes, and Tuyet mentions a scream -- likely because the crowd heard it too and she couldn't contradict their witness accounts. I bet Tuyet was trying to use a more effective means of killing (to make sure the body remained for the tablet), but this Matoran screamed and drew witnesses, so Tuyet had to quickly drown the Matoran and then make it look like she tried to rescue a drowning Matoran. If such a scenario did happen, after all, a drowning death is exactly what you'd expect from a murderous Toa of Water, and I would not expect a Toa of Water who's murdering to
intentionally use drowning as a method (as that would too obviously draw attention to her). Interesting...
And then Lhikan confronts her. I skimmed some parts but I'm pretty sure it was only those three victims. It can all fit quite naturally on close examination.

I'd even say that once again it appears Greg had planned this well in advance of this story, as he includes exactly the right details to make it fit this easily. Note that this was posted in 2007, at a time when we've already concluded he had almost certainly decided this.
