For what it’s worth, I read this comment as constructive rather than non-constructive.
If I write a long report and an expert in the field think that the entire premise is flawed for specific technical reasons, I’d much rather them point this out rather than for them to worry about niceness and then never getting around to mentioning it, thus causing my report to languish in obscurity without me knowing why (or worse, for my false research to actually be used!)
For what it’s worth, I read this comment as constructive rather than non-constructive.
If I write a long report and an expert in the field think that the entire premise is flawed for specific technical reasons, I’d much rather them point this out rather than for them to worry about niceness and then never getting around to mentioning it, thus causing my report to languish in obscurity without me knowing why (or worse, for my false research to actually be used!)