Mac app store behaves differently when on Ethernet than on wifi

Hi, I purchased mountain lion and I'm having difficulties downloading the app because the Internet connection in my area isn't reliable and I always get errors for dropped connection which is sometimes force me to redownload the whole app after downloading more than 1gb. Anyway, I cam across apple's support website for an article concerning resuming downloads on the Mac app store. At the end of the article, apple wrote a note that it's preferred to use Ethernet. After multiple trials, I connected my Mac ethernetly to the Internet by connecting a cable from the Internet router to my Mac since other part of the family still needs the wifi. What I first realized is that when I did that, that when I disconnect the Internet or the router turn off, the download doesn't display an on screen error concerning the dropped connection. However the download turns into "waiting..." and when I reconnect again it refreshes the purchased page and automatically resume the download which actually doesn't happen over wifi. Whereas over wifi I always had errors and I had to press retry and stuff in order to resume my download. In addition, concerning the resuming of a downloading app, over wifi it seldomly resume from where I left the download and I realized that when I download like 4 mb over wifi and pause the download, it restarts all over again whereas by Ethernet it resume right from the few mb. So I just wanna know why it's happening and acting like that?