The difference here is that the excel errors are systematic so should be more easily avoidable, whereas long hand calcs are more varied and harder to correct.
I use Excel a lot. These things don't trip me up in my field. Could it be that this field is a rather niche use case, and therefore the users should learn to watch out for them?
One in five genetics papers have errors caused by mistakes in the use of Excel
As if longhand calculations never have errors?