Stating surprise about another researcher in my talk
Talk about the work. Stick to the facts.

Clearly and bluntly stating the limitations of a result is fine, but criticism of a researcher during a research talk is completely inappropriate.  Your expression of surprise could be taken as criticism of either the researcher's ethics or their competence, neither of which is appropriate to air in front of a research audience.

Whether the researcher is junior or senior is irrelevant.  Whether the researcher is known to your audience or not is irrelevant.  Criticism should be delivered privately.