I find this hard to believe.
This is being reported by the parents to the researchers. Parents are not medical personnel.
The conversation was probably like this( and I have witnessed this)- “Your child is terminal- and will probably die in the next two days. In order to make your child comfortable, we will need to give morphine. Sometimes large doses of morphine can stop breathing, but your child needs the morphine to be comfortable.”
The parents then interpret this as euthanasia. Not true.
That is a really good point. What you describe is a dangerous attempt at palliative care.
Euthanasia is the deliberate attempt at painless killing with the objective of causing death.