Are you using the progress bar for the upload or just the default upload settings (ie blank screen)?

If you are using the progress bar then the upload limit is controlled inside /ubr/ directory. It could be that one setting somewhere is limiting calculation but another is allowing the big file. But in 2.8 I don't think that exists anymore.

My personal experience is that the /ubr/ settings will limit the uploads right away. You have to manually change the text in the upload_file.tpl file to tell people the limit.