I think the problem is that there isn't really any compelling evidence to suggest that men are more drawn to engineering because of biology. I would actually invert your last paragraph: there are so many plausible extrinsic reasons that men are more likely to go into STEM than women that it doesn't make sense to try to explain away these gender gaps as being due to some intrinsic difference.
I think it's fair to say that you can believe that the difference is biological without it being sexist. But it is also true that many people who hold this belief are sexist (in fact most misogynists probably do believe this), so people being hesitant to give a platform to people taking this angle is understandable.
I think it's fair to say that you can believe that the difference is biological without it being sexist. But it is also true that many people who hold this belief are sexist (in fact most misogynists probably do believe this), so people being hesitant to give a platform to people taking this angle is understandable.