The original dictionary was printed with simplified characters only, ok? So in order for Pleco to display the dictionary with traditional characters, they had to convert from simplified to traditional. Rather than doing it all by hand (A very time-consuming, expensive process!) they'll automate most of it, and tweak the results so they're accurate. I'm not sure if they've had time to do it yet, though.
An example is something like 前边 - the entry for that is simply [名] 前面. However, the software is not guaranteed to know that 前面 is also how it would be written with traditional characters. For example, another way to write 面 is 麵. While we know that it should be 前面, not 前麵, the software may not, and so it may not be correct until Pleco has had a chance to tweak it. In this particular example, it's correct, but there may be others which aren't.
Other examples would be 后/後, or 表/錶.
Does that help any?