The less atmosphere between you and the sun, the more radiation you'll experience. There was definitely less atmosphere between the remains and the sun in this case than if they were shipped by plane, making the radiation higher.
And if they were shipped somewhere by plane during normal transport by academics, they would have taken the appropriate steps to ensure the preservation of the sample.
I can't say I really understand why some people seem so surprised that the scientists would be unhappy at this, or feel like they scientists are being unreasonable here. Their whole job is to learn as much as they can from what samples we can recover from the past for the benefit of humanity's understanding, and a priceless sample was needlessly handled in a way that may make it useless to their studies, because a billionaire though it would be entertaining to shoot it into space for no real reason...
In what world would they not be unhappy with this situation?