No one says "wasted their precious time" in a sincere apology. The word 'precious' here is exclusively used for sarcasm in the context of an apology, as it does not represent a specific technical term such as might appear in a gemology apology.
If they have a problem in mastering English, they can take lessons, and make native speaker review their communication in the meantime.
The benefit of the doubt can not stick for ever on people caught red-handed. It can be restored of course, but they are now in a position where they drastically shifted the perception by their own actions, and thus can't really complain of the results of their own doings. Yes, they can not make mistakes anymore, and everything they did in the past will be reviewed harshly, not for further condemning them without reasons, but just to be sure they did not actually break things while practicing their malicious activities.
If I can come up with the scientific paper gibberish for that in real-time, and I don’t even write science papers, then these people who understand how to navigate an ethical review board process surely know how to massage an unpleasant truth into dry and dusty wording.
I think that they just screwed up and missed the word “precious” in editing, and thus got caught being dismissive and snide towards their experiment’s participants. Without that word, it’s a plausible enough paragraph. With it, it’s no longer plausibly innocent.