Will it be hard for people to write technical reports if you are good at math but bad at essay writing?

Answer 1

Maybe not, but it could end up being a poor report which nobody wants to read! And that could affect the author's prospects adversely.

I used to get a lot of reports and would not read a poorly written one. If the person writing it cannot be bothered enough to put the effort into writing it properly then I was certainly not going to put in the time nor effort to try and work out what the report should have said.