And potentially altered by having been unnecessarily put through extremely abnormal treatment, meaning any conclusions you draw from studying them are muddied by having been blasted out into space, regardless of having come back.

Folks have brought up that taking them into space exposes them to high levels of radiation, and the proper steps may not have been taken to protect the remains from said radiation. Folks have argued that because they were in a craft, that they won’t have been exposed to any radiation, but thats not how that works- people who take a flight on a regular airplane are exposed to higher levels of radiation, nevermind spacecraft. Taking the remains into space needlessly reduces their value to scientists who may have learned things from them, and now what they learn may not be meaningful or helpful, because the remains were handled so unusually.

It was entirely unnecessary, nothing was gained by having done it, and it has a cost to science, so the scientists are unhappy- that hardly seems unsurprising.