There was no mention of lots several requirements. If the OP didn’t state all detail lines will be the same height, it’s good practice to assume there may be growth (and then ask).
Nor was any mention made of not using them, but I wouldn't really expect there to be. I found that I nearly always had to allow the detail section to grow. That could be because, in my line of work, we do use quite long winded scientific terminology. Until the OP provides more info I'd play safe, and assume that they are allowing the section to grow.
let’s wait and see - if the OP required the blank rows on a printout for users to write additional data for later input I can understand it - the blank rows might contain a line as a delimiter. But that does not appear to be the case here.